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OPTIMIZING ANDROID UI PRO TIPS FOR CREATING SMOOTH AND RESPONSIVE APPS

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@CYRILMOTTIER

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GET TO KNOW JAVA

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DON’T USE BOXED TYPES UNNECESSARILY

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HashMap hashMap = new HashMap(); hashMap.put(665, "Android"); hashMap.put(666, "rocks"); hashMap.get(666);

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HashMap< , String> hashMap = new HashMap< , String>(); hashMap.put(665, "Android"); hashMap.put(666, "rocks"); hashMap.get(666); Integer Integer Integer is not int

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new Integer(666) REALITY BECOMES 666 666 DREAMS

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QUESTION Would the result have been the same if we had been trying to add ″Android″ with 42 as key?

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QUESTION Would the result have been the same if we had been trying to add ″Android″ with 42 as key? ANSWER Yes 42 is the answer to the Java universe

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QUESTION Would the result have been the same if we had been trying to add ″Android″ with 42 as key? ANSWER Yes 42 is the anwser to the Java universe I AM JOKING

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QUESTION Would the result have been the same if we had been trying to add ″Android″ with 42 as key? ANSWER No Integer has an internal cache for [-128, 127]

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SparseArray: SparseArrays map integers to Objects. Unlike a normal array of Objects, there can be gaps in the indices. It is intended to be more efficient than using a HashMap to map Integers to Objects.

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SparseArray sparseArray = new SparseArray(); sparseArray.put(665, "Android"); sparseArray.put(666, "rocks"); sparseArray.get(666);

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SparseArray sparseArray = new SparseArray(); sparseArray.put(665, "Android"); sparseArray.put(666, "rocks"); sparseArray.get(666); ints as keys, Strings as values

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SparseArray sparseArray = new SparseArray(); sparseArray.put(665, "Android"); sparseArray.put(666, "rocks"); sparseArray.get(666); no autoboxing, at all ints as keys, Strings as values

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REUSE AS MUCH AS POSSIBLE

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@Override public View getView(int position, View convertView, ViewGroup parent) { final View itemView = mInflater.inflate( android.R.layout.two_line_list_item, // resource parent, // parent false); // attach ((TextView) itemView.findViewById(android.R.id.text1)) .setText(TITLES.get(position)); ((TextView) itemView.findViewById(android.R.id.text2)) .setText(SUBTITLES.get(position)); return itemView; } NEVER DO THIS !!!

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@Override public View getView(int position, View convertView, ViewGroup parent) { ((TextView) itemView.findViewById(android.R.id.text1)) .setText(TITLES.get(position)); ((TextView) itemView.findViewById(android.R.id.text2)) .setText(SUBTITLES.get(position)); return itemView; } NEVER DO THIS !!! android.R.layout.two_line_list_item, // resource false); // attach final View itemView = mInflater.inflate( parent, // parent inflate a new View at every getView call

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convertView: The old view to reuse, if possible. Note: You should check that this view is non-null and of an appropriate type before using. If it is not possible to convert this view to display the correct data, this method can create a new view.

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(RE)USE THE CONVERTVIEW @Override public View getView(int position, View convertView, ViewGroup parent) { if (convertView == null) { convertView = mInflater.inflate( android.R.layout.two_line_list_item, // resource parent, // parent false); // attach } ((TextView) convertView.findViewById(android.R.id.text1)) .setText(TITLES.get(position)); ((TextView) convertView.findViewById(android.R.id.text2)) .setText(SUBTITLES.get(position)); return convertView; }

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(RE)USE THE CONVERTVIEW @Override public View getView(int position, View convertView, ViewGroup parent) { if (convertView == null) { convertView = mInflater.inflate( android.R.layout.two_line_list_item, // resource parent, // parent false); // attach } ((TextView) convertView.findViewById(android.R.id.text1)) .setText(TITLES.get(position)); ((TextView) convertView.findViewById(android.R.id.text2)) .setText(SUBTITLES.get(position)); return convertView; } check for a convertView

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(RE)USE THE CONVERTVIEW @Override public View getView(int position, View convertView, ViewGroup parent) { if (convertView == null) { convertView = mInflater.inflate( android.R.layout.two_line_list_item, // resource parent, // parent false); // attach } ((TextView) convertView.findViewById(android.R.id.text1)) .setText(TITLES.get(position)); ((TextView) convertView.findViewById(android.R.id.text2)) .setText(SUBTITLES.get(position)); return convertView; } create a view only when necessary check for a convertView

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PREFER STATIC FACTORY METHODS TO CONSTRUCTORS

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private static final int MSG_ANIMATION_FRAME = 0xcafe; public void sendMessage(Handler handler, Object userInfo) { final Message message = new Message(); message.what = MSG_ANIMATION_FRAME; message.obj = userInfo; handler.sendMessage(message); }

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private static final int MSG_ANIMATION_FRAME = 0xcafe; public void sendMessage(Handler handler, Object userInfo) { final Message message = Message(); message.what = MSG_ANIMATION_FRAME; message.obj = userInfo; handler.sendMessage(message); } new creation of a new Message instance

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private static final int MSG_ANIMATION_FRAME = 0xcafe; public void sendMessage(Handler handler, Object userInfo) { final Message message = Message.obtain(); message.what = MSG_ANIMATION_FRAME; message.obj = userInfo; handler.sendMessage(message); }

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private static final int MSG_ANIMATION_FRAME = 0xcafe; public void sendMessage(Handler handler, Object userInfo) { final Message message = Message.obtain(); message.what = MSG_ANIMATION_FRAME; message.obj = userInfo; handler.sendMessage(message); } try to reuse Message instances Message.obtain(): Gets an object from a pool or create a new one

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Want this in your app? Go to github.com/android/platform_frameworks_base Find android.util Copy PoolableManager, Pool, Poolable, Pools, FinitePool, etc. Paste in your project Enjoy the easy-to-use object pooling mechanism

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PREFER STATIC VARIABLES TO TEMPORARY VARIABLES

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@Override public boolean onInterceptTouchEvent(MotionEvent event) { final int x = (int) event.getX(); final int y = (int) event.getY(); final Rect frame = new Rect(); // Are we touching mHost ? mHost.getHitRect(frame); if (!frame.contains(x, y)) { return false; } return true; }

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@Override public boolean onInterceptTouchEvent(MotionEvent event) { final int x = (int) event.getX(); final int y = (int) event.getY(); final Rect frame = Rect(); // Are we touching mHost ? mHost.getHitRect(frame); if (!frame.contains(x, y)) { return false; } return true; } creation of a new Rect instance new

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private final Rect mFrameRect = new Rect(); @Override public boolean onInterceptTouchEvent(MotionEvent event) { final int x = (int) event.getX(); final int y = (int) event.getY(); final Rect frame = mFrameRect; // Are we touching mHost ? mHost.getHitRect(frame); if (!frame.contains(x, y)) { return false; } return true; }

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private final Rect mFrameRect = new Rect(); @Override public boolean onInterceptTouchEvent(MotionEvent event) { final int x = (int) event.getX(); final int y = (int) event.getY(); final Rect frame = mFrameRect; // Are we touching mHost ? mHost.getHitRect(frame); if (!frame.contains(x, y)) { return false; } return true; } create a single Rect

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private final Rect mFrameRect = new Rect(); @Override public boolean onInterceptTouchEvent(MotionEvent event) { final int x = (int) event.getX(); final int y = (int) event.getY(); final Rect frame = mFrameRect; // Are we touching mHost ? mHost.getHitRect(frame); if (!frame.contains(x, y)) { return false; } return true; } create a single Rect always use the same instance of Rect

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REMEMBER STRINGS ARE ELLIGIBLE TO GARBAGE COLLECTION

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public class CharArrayBufferAdapter extends CursorAdapter { private interface DataQuery { int TITLE = 0; int SUBTITLE = 1; } public CharArrayBufferAdapter(Context context, Cursor c) { super(context, c); } @Override public void bindView(View view, Context context, Cursor cursor) { final TwoLineListItem item = (TwoLineListItem) view; item.getText1().setText(cursor.getString(DataQuery.TITLE)); item.getText2().setText(cursor.getString(DataQuery.SUBTITLE)); } @Override public View newView(Context context, Cursor cursor, ViewGroup parent) { return LayoutInflater.from(context).inflate( android.R.layout.two_line_list_item, parent, false); } }

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public class CharArrayBufferAdapter extends CursorAdapter { private interface DataQuery { int TITLE = 0; int SUBTITLE = 1; } public CharArrayBufferAdapter(Context context, Cursor c) { super(context, c); } @Override public void bindView(View view, Context context, Cursor cursor) { final TwoLineListItem item = (TwoLineListItem) view; item.getText1().setText( ); item.getText2().setText( ); } @Override public View newView(Context context, Cursor cursor, ViewGroup parent) { return LayoutInflater.from(context).inflate( android.R.layout.two_line_list_item, parent, false); } } cursor.getString(DataQuery.TITLE) cursor.getString(DataQuery.SUBTITLE) getString means new String

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private static class ViewHolder { CharArrayBuffer titleBuffer = new CharArrayBuffer(128); CharArrayBuffer subtitleBuffer = new CharArrayBuffer(128); } @Override public void bindView(View view, Context context, Cursor cursor) { final TwoLineListItem item = (TwoLineListItem) view; final ViewHolder holder = (ViewHolder) view.getTag(); final CharArrayBuffer titleBuffer = holder.titleBuffer; cursor.copyStringToBuffer(DataQuery.TITLE, titleBuffer); item.getText1().setText(titleBuffer.data, 0, titleBuffer.sizeCopied); final CharArrayBuffer subtitleBuffer = holder.titleBuffer; cursor.copyStringToBuffer(DataQuery.SUBTITLE, subtitleBuffer); item.getText2().setText(subtitleBuffer.data, 0, subtitleBuffer.sizeCopied); } @Override public View newView(Context context, Cursor cursor, ViewGroup parent) { final View v = LayoutInflater.from(context).inflate( android.R.layout.two_line_list_item, parent, false); v.setTag(new ViewHolder()); return v; }

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private static class ViewHolder { CharArrayBuffer titleBuffer = new CharArrayBuffer(128); CharArrayBuffer subtitleBuffer = new CharArrayBuffer(128); } @Override public void bindView(View view, Context context, Cursor cursor) { final TwoLineListItem item = (TwoLineListItem) view; final ViewHolder holder = (ViewHolder) view.getTag(); final CharArrayBuffer titleBuffer = holder.titleBuffer; cursor.copyStringToBuffer(DataQuery.TITLE, titleBuffer); item.getText1().setText(titleBuffer.data, 0, titleBuffer.sizeCopied); final CharArrayBuffer subtitleBuffer = holder.titleBuffer; cursor.copyStringToBuffer(DataQuery.SUBTITLE, subtitleBuffer); item.getText2().setText(subtitleBuffer.data, 0, subtitleBuffer.sizeCopied); } @Override public View newView(Context context, Cursor cursor, ViewGroup parent) { final View v = LayoutInflater.from(context).inflate( android.R.layout.two_line_list_item, parent, false); v.setTag(new ViewHolder()); return v; } attach buffers to the itemview

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private static class ViewHolder { CharArrayBuffer titleBuffer = new CharArrayBuffer(128); CharArrayBuffer subtitleBuffer = new CharArrayBuffer(128); } @Override public void bindView(View view, Context context, Cursor cursor) { final TwoLineListItem item = (TwoLineListItem) view; final ViewHolder holder = (ViewHolder) view.getTag(); final CharArrayBuffer titleBuffer = holder.titleBuffer; cursor.copyStringToBuffer(DataQuery.TITLE, titleBuffer); item.getText1().setText(titleBuffer.data, 0, titleBuffer.sizeCopied); final CharArrayBuffer subtitleBuffer = holder.titleBuffer; cursor.copyStringToBuffer(DataQuery.SUBTITLE, subtitleBuffer); item.getText2().setText(subtitleBuffer.data, 0, subtitleBuffer.sizeCopied); } @Override public View newView(Context context, Cursor cursor, ViewGroup parent) { final View v = LayoutInflater.from(context).inflate( android.R.layout.two_line_list_item, parent, false); v.setTag(new ViewHolder()); return v; } attach buffers to the itemview get the buffers

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private static class ViewHolder { CharArrayBuffer titleBuffer = new CharArrayBuffer(128); CharArrayBuffer subtitleBuffer = new CharArrayBuffer(128); } @Override public void bindView(View view, Context context, Cursor cursor) { final TwoLineListItem item = (TwoLineListItem) view; final ViewHolder holder = (ViewHolder) view.getTag(); final CharArrayBuffer titleBuffer = holder.titleBuffer; cursor.copyStringToBuffer(DataQuery.TITLE, titleBuffer); item.getText1().setText(titleBuffer.data, 0, titleBuffer.sizeCopied); final CharArrayBuffer subtitleBuffer = holder.titleBuffer; cursor.copyStringToBuffer(DataQuery.SUBTITLE, subtitleBuffer); item.getText2().setText(subtitleBuffer.data, 0, subtitleBuffer.sizeCopied); } @Override public View newView(Context context, Cursor cursor, ViewGroup parent) { final View v = LayoutInflater.from(context).inflate( android.R.layout.two_line_list_item, parent, false); v.setTag(new ViewHolder()); return v; } attach buffers to the itemview get the buffers copy column content to buffer

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private static class ViewHolder { CharArrayBuffer titleBuffer = new CharArrayBuffer(128); CharArrayBuffer subtitleBuffer = new CharArrayBuffer(128); } @Override public void bindView(View view, Context context, Cursor cursor) { final TwoLineListItem item = (TwoLineListItem) view; final ViewHolder holder = (ViewHolder) view.getTag(); final CharArrayBuffer titleBuffer = holder.titleBuffer; cursor.copyStringToBuffer(DataQuery.TITLE, titleBuffer); item.getText1().setText(titleBuffer.data, 0, titleBuffer.sizeCopied); final CharArrayBuffer subtitleBuffer = holder.titleBuffer; cursor.copyStringToBuffer(DataQuery.SUBTITLE, subtitleBuffer); item.getText2().setText(subtitleBuffer.data, 0, subtitleBuffer.sizeCopied); } @Override public View newView(Context context, Cursor cursor, ViewGroup parent) { final View v = LayoutInflater.from(context).inflate( android.R.layout.two_line_list_item, parent, false); v.setTag(new ViewHolder()); return v; } attach buffers to the itemview get the buffers set the buffer to the TextView copy column content to buffer

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FLATTEN VIEW HIERARCHIES

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PERFECTLY MASTER THE ANDROID UI TOOLKIT

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1 2 3 GridLayout RelativeLayout

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1GridLayout A Layout that places its children in a rectangular grid

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1GridLayout 12 VIEWS

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1GridLayout 12 VIEWS 9 VIEWS

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2 RelativeLayout A Layout where the positions of the children can be described in relation to each other or to the parent.

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2 RelativeLayout A Layout where the positions of the children can be described in relation to each other or to the parent. Flatten hierarchy

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3

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3 INVALID XML DOCUMENT

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3

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3 useless ViewGroup

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3

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COOK YOUR OWN VIEWS WHENEVER NECESSARY

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goo.gl/ZQIZ4 AVélov beta

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ListView’s padding

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QUESTION What are the available techniques to create such a a great ListView header?

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public class UnderlinedTextView extends TextView { private final Paint mPaint = new Paint(); private int mUnderlineHeight; public UnderlinedTextView(Context context) { super(context); } public UnderlinedTextView(Context context, AttributeSet attrs) { super(context, attrs); } public UnderlinedTextView(Context context, AttributeSet attrs, int defStyle) { super(context, attrs, defStyle); } }

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public class UnderlinedTextView extends TextView { private final Paint mPaint = new Paint(); private int mUnderlineHeight; public UnderlinedTextView(Context context) { super(context); } public UnderlinedTextView(Context context, AttributeSet attrs) { super(context, attrs); } public UnderlinedTextView(Context context, AttributeSet attrs, int defStyle) { super(context, attrs, defStyle); } } extends TextView

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@Override public void setPadding(int left, int top, int right, int bottom) { super.setPadding(left, top, right, mUnderlineHeight + bottom); } public void setUnderlineHeight(int underlineHeight) { if (underlineHeight < 0) underlineHeight = 0; if (underlineHeight != mUnderlineHeight) { mUnderlineHeight = underlineHeight; setPadding(getPaddingLeft(), getPaddingTop(), getPaddingRight(), getPaddingBottom() + mUnderlineHeight); } } public void setUnderlineColor(int underlineColor) { if (mPaint.getColor() != underlineColor) { mPaint.setColor(underlineColor); invalidate(); } } @Override protected void onDraw(Canvas canvas) { super.onDraw(canvas); canvas.drawRect(0, getHeight() - mUnderlineHeight, getWidth(), getHeight(), mPaint); }

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@Override public void setPadding(int left, int top, int right, int bottom) { super.setPadding(left, top, right, mUnderlineHeight + bottom); } public void setUnderlineHeight(int underlineHeight) { if (underlineHeight < 0) underlineHeight = 0; if (underlineHeight != mUnderlineHeight) { mUnderlineHeight = underlineHeight; setPadding(getPaddingLeft(), getPaddingTop(), getPaddingRight(), getPaddingBottom() + mUnderlineHeight); } } public void setUnderlineColor(int underlineColor) { if (mPaint.getColor() != underlineColor) { mPaint.setColor(underlineColor); invalidate(); } } @Override protected void onDraw(Canvas canvas) { super.onDraw(canvas); canvas.drawRect(0, getHeight() - mUnderlineHeight, getWidth(), getHeight(), mPaint); } use padding to avoid measurements use padding to avoid measurements

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@Override public void setPadding(int left, int top, int right, int bottom) { super.setPadding(left, top, right, mUnderlineHeight + bottom); } public void setUnderlineHeight(int underlineHeight) { if (underlineHeight < 0) underlineHeight = 0; if (underlineHeight != mUnderlineHeight) { mUnderlineHeight = underlineHeight; setPadding(getPaddingLeft(), getPaddingTop(), getPaddingRight(), getPaddingBottom() + mUnderlineHeight); } } public void setUnderlineColor(int underlineColor) { if (mPaint.getColor() != underlineColor) { mPaint.setColor(underlineColor); invalidate(); } } @Override protected void onDraw(Canvas canvas) { super.onDraw(canvas); canvas.drawRect(0, getHeight() - mUnderlineHeight, getWidth(), getHeight(), mPaint); } extend TextView default behavior use padding to avoid measurements use padding to avoid measurements

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DEVELOPERS TEND TO BE «NEVER SATISFIED» PEOPLE THAT ARE ALWAYS ASKING FOR MORE ASSERTION Yep, this is the exact same definition of «being French»

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VIEW & have been designed to be easily extended via inheritance VIEWGROUP

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GET OFF THE MAIN THREAD

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DON’T BLOCK THE MAIN THREAD

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THE MAIN THREAD IS WHERE ALL EVENTS ARE DISPATCHED TRUE FACT

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EVENT QUEUE EVENT LOOP

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EVENT QUEUE EVENT LOOP

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onMeasure onLayout onDrawn onTouchEvent BE MINDFUL WITH CRITICAL METHODS

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3 disc network hardware MAIN OPERATIONS to perform in background

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MOVE WORK OFF THE MAIN THREAD

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THE JAVA WAY... Plain old Java java.util.concurrent

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THE JAVA WAY... Plain old Java java.util.concurrent FOR BEARDED MEN ONLY

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YOU ARE MORE THIS KIND OF GUY?

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THE ANDROID WAY... Handler AsyncTask Loader IntentService

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DO LESS AND APPROPRIATELY

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CACHE VALUES NOT TO OVER COMPUTE THEM

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@Override public View getView(int position, View convertView, ViewGroup parent) { if (convertView == null) { convertView = mInflater.inflate( android.R.layout.two_line_list_item, // resource parent, // parent false); // attach } ((TextView) convertView.findViewById(android.R.id.text1)) .setText(TITLES.get(position)); ((TextView) convertView.findViewById(android.R.id.text2)) .setText(SUBTITLES.get(position)); return convertView; } DO YOU REMEMBER THIS?

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QUESTION How to avoid having findViewById executed at every call to getView?

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QUESTION How to avoid having findViewById executed at every call to getView? ANSWER Caching it!

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static class ViewHolder { TextView text1; TextView text2; } VIEW HOLDER

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@Override public View getView(int position, View convertView, ViewGroup parent) { ViewHolder holder; if (convertView == null) { convertView = mInflater.inflate( android.R.layout.two_line_list_item, parent, false); holder = new ViewHolder(); holder.text1 = (TextView) convertView.findViewById(android.R.id.text1); holder.text2 = (TextView) convertView.findViewById(android.R.id.text2); convertView.setTag(holder); } else { holder = (ViewHolder) convertView.getTag(); } holder.text1.setText(STRINGS.get(position)); holder.text2.setText(STRINGS.get(position)); return convertView; } AVOID REPETITIVE EXECUTIONS

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@Override public View getView(int position, View convertView, ViewGroup parent) { ViewHolder holder; if (convertView == null) { convertView = mInflater.inflate( android.R.layout.two_line_list_item, parent, false); holder = new ViewHolder(); holder.text1 = (TextView) convertView.findViewById(android.R.id.text1); holder.text2 = (TextView) convertView.findViewById(android.R.id.text2); convertView.setTag(holder); } else { holder = (ViewHolder) convertView.getTag(); } holder.text1.setText(STRINGS.get(position)); holder.text2.setText(STRINGS.get(position)); return convertView; } AVOID REPETITIVE EXECUTIONS cache refs to the children

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@Override public View getView(int position, View convertView, ViewGroup parent) { ViewHolder holder; if (convertView == null) { convertView = mInflater.inflate( android.R.layout.two_line_list_item, parent, false); holder = new ViewHolder(); holder.text1 = (TextView) convertView.findViewById(android.R.id.text1); holder.text2 = (TextView) convertView.findViewById(android.R.id.text2); convertView.setTag(holder); } else { holder = (ViewHolder) convertView.getTag(); } holder.text1.setText(STRINGS.get(position)); holder.text2.setText(STRINGS.get(position)); return convertView; } AVOID REPETITIVE EXECUTIONS cache refs to the children retrieve cached refs

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@Override public View getView(int position, View convertView, ViewGroup parent) { ViewHolder holder; if (convertView == null) { convertView = mInflater.inflate( android.R.layout.two_line_list_item, parent, false); holder = new ViewHolder(); holder.text1 = (TextView) convertView.findViewById(android.R.id.text1); holder.text2 = (TextView) convertView.findViewById(android.R.id.text2); convertView.setTag(holder); } else { holder = (ViewHolder) convertView.getTag(); } holder.text1.setText(STRINGS.get(position)); holder.text2.setText(STRINGS.get(position)); return convertView; } AVOID REPETITIVE EXECUTIONS cache refs to the children retrieve cached refs use cached refs

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GIVE PRORITITY TO YOUR THREADS

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private static final int MSG_LOAD = 0xbeef; private Handler mHandler = new Handler(Looper.getMainLooper()); public void loadUrl(final String url) { new Thread(new Runnable() { @Override public void run() { Process.setThreadPriority(Process.THREAD_PRIORITY_BACKGROUND); InputStream i = null; Bitmap b = null; try { i = new URL(url).openStream(); b = BitmapFactory.decodeStream(i); } catch (Exception e) { } finally { if (i != null) try { i.close(); } catch (IOException e) {} } Message.obtain(mHandler, MSG_LOAD, b).sendToTarget(); } }).start(); }

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private static final int MSG_LOAD = 0xbeef; private Handler mHandler = new Handler(Looper.getMainLooper()); public void loadUrl(final String url) { new Thread(new Runnable() { @Override public void run() { Process.setThreadPriority(Process.THREAD_PRIORITY_BACKGROUND); InputStream i = null; Bitmap b = null; try { i = new URL(url).openStream(); b = BitmapFactory.decodeStream(i); } catch (Exception e) { } finally { if (i != null) try { i.close(); } catch (IOException e) {} } Message.obtain(mHandler, MSG_LOAD, b).sendToTarget(); } }).start(); } set a low priority

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private static final int MSG_LOAD = 0xbeef; private Handler mHandler = new Handler(Looper.getMainLooper()); public void loadUrl(final String url) { new Thread(new Runnable() { @Override public void run() { Process.setThreadPriority(Process.THREAD_PRIORITY_BACKGROUND); InputStream i = null; Bitmap b = null; try { i = new URL(url).openStream(); b = BitmapFactory.decodeStream(i); } catch (Exception e) { } finally { if (i != null) try { i.close(); } catch (IOException e) {} } Message.obtain(mHandler, MSG_LOAD, b).sendToTarget(); } }).start(); } set a low priority post a Message to callback the UI Thread

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FAVOR UI TO BACKGROUND COMPUTATIONS

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SCROLL STATES 3 ListView can have The current ListView’s scroll state can be obtained using an OnScrollListener

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1 2 3 IDLE TOUCH SCROLL FLING

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1IDLE The view is not scrolling

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2TOUCH SCROLL The user is scrolling using touch, and their finger is still on the screen

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3FLING The user had previously been scrolling using touch and had performed a fling. The animation is now coasting to a stop Avoid blocking the animation pause worker Threads

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getListView().setOnScrollListener(mScrollListener); private OnScrollListener mScrollListener = new OnScrollListener() { @Override public void onScrollStateChanged(AbsListView view, int scrollState) { ImageLoader imageLoader = ImageLoader.get(getContext()); imageLoader.setPaused(scrollState == OnScrollListener.SCROLL_STATE_FLING); } @Override public void onScroll(AbsListView view, int firstVisibleItem, int visibleItemCount, int totalItemCount) { // Nothing to do } };

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getListView().setOnScrollListener(mScrollListener); private OnScrollListener mScrollListener = new OnScrollListener() { @Override public void onScrollStateChanged(AbsListView view, int scrollState) { ImageLoader imageLoader = ImageLoader.get(getContext()); imageLoader.setPaused(scrollState == OnScrollListener.SCROLL_STATE_FLING); } @Override public void onScroll(AbsListView view, int firstVisibleItem, int visibleItemCount, int totalItemCount) { // Nothing to do } }; set the listener

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getListView().setOnScrollListener(mScrollListener); private OnScrollListener mScrollListener = new OnScrollListener() { @Override public void onScrollStateChanged(AbsListView view, int scrollState) { ImageLoader imageLoader = ImageLoader.get(getContext()); imageLoader.setPaused(scrollState == OnScrollListener.SCROLL_STATE_FLING); } @Override public void onScroll(AbsListView view, int firstVisibleItem, int visibleItemCount, int totalItemCount) { // Nothing to do } }; (un)pause ImageLoader set the listener

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CONCLUSION

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DO NOT BLOCK THE MAIN THREAD

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FLATTEN YOUR VIEW HIERARCHY

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LAZY LOAD AND REUSE WHENEVER POSSIBLE

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PRIORITIZE TASKS: UI ALWAYS COMES FIRST

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CYRIL MOTTIER @cyrilmottier android.cyrilmottier.com