2023年7月13日发(作者：)

AndroidKeyEvent分发过程⼀、背景Activity和View有三个override的⽅法dispatchKeyEvent、onKeyUp、onKeyDown，其中View还有⼀个setOnKeyListener⽅法。只知道这⼏个⽅法是设置处理key event的，但是⼀直不太理解这⼏个⽅法的作⽤和相互影响。所以准备写个demo彻底搞清楚这⼏个⽅法的作⽤和原理。⼆、测试准备新建三个类public class KeyDispatchDemo extends Activity { @Override protected void onCreate(Bundle savedInstanceState) { te(savedInstanceState); setContentView(ty_key_dispatch); } @Override public boolean dispatchKeyEvent(KeyEvent event) { Log.d("Activity", "dispatchKeyEvent: " + ion() + " | " + Code()); return chKeyEvent(event); } @Override public boolean onKeyUp(int keyCode, KeyEvent event) { Log.d("Activity", "onKeyUp: " + keyCode); return p(keyCode, event); } @Override public boolean onKeyDown(int keyCode, KeyEvent event) { Log.d("Activity", "onKeyDown: " + keyCode); return own(keyCode, event); }}public class KeyDispatchLinearLayout extends LinearLayout { public KeyDispatchLinearLayout(Context context) { super(context); } public KeyDispatchLinearLayout(Context context, @Nullable AttributeSet attrs) { super(context, attrs); } public KeyDispatchLinearLayout(Context context, @Nullable AttributeSet attrs, int defStyleAttr) { super(context, attrs, defStyleAttr); } @Override public boolean dispatchKeyEvent(KeyEvent event) { Log.d("ViewGroup", "dispatchKeyEvent: " + ion() + " | " + Code()); return chKeyEvent(event); } @Override public boolean onKeyUp(int keyCode, KeyEvent event) { Log.d("ViewGroup", "onKeyUp: " + keyCode); return p(keyCode, event); } @Override public boolean onKeyDown(int keyCode, KeyEvent event) { Log.d("ViewGroup", "onKeyDown: " + keyCode); return own(keyCode, event); }}public class KeyDispatchView extends View { public KeyDispatchView(Context context) { super(context); } public KeyDispatchView(Context context, @Nullable AttributeSet attrs) { super(context, attrs); } public KeyDispatchView(Context context, @Nullable AttributeSet attrs, int defStyleAttr) { super(context, attrs, defStyleAttr); } @Override public boolean dispatchKeyEvent(KeyEvent event) { Log.d("View", "dispatchKeyEvent: " + ion() + " | " + Code()); return chKeyEvent(event); } @Override public boolean onKeyUp(int keyCode, KeyEvent event) { Log.d("View", "onKeyUp: " + keyCode); return p(keyCode, event); } @Override public boolean onKeyDown(int keyCode, KeyEvent event) { Log.d("View", "onKeyDown: " + keyCode); return own(keyCode, event); }}布局⽂件： 三、Key event分发流程分析⾸先在关键⽅法上都打上断点，按下键盘，发出⼀个key event事件。1、dispatchKeyEvent的执⾏流程dispatchKeyEvent的分发主要是：DecorView——>Activity——>ViewGroup——>View⼀个Key event是⾸先传到DecorView中，DecorView通过下⾯的代码分发给Activity： if (!royed()) { final ck cb = lback(); final boolean handled = cb != null && mFeatureId < 0 ? chKeyEvent(event) : chKeyEvent(event); if (handled) { return true; } }其中lback()就是⽬标Activity在Activity的dispatchKeyEvent⽅法⾥⾯，传递给了PhoneWindow的superDispatchKeyEvent⽅法PhoneWindow的superDispatchKeyEvent⽅法会调到ViewGroup的dispatchKeyEvent⽅法：ViewGroup会⼀层⼀层的把key event传递给持有焦点的child：总结：在这个dispatchKeyEvent链中，只要有⼀个返回true，就是没调chKeyEvent⽅法，那么key event的传递就会终⽌。2、onKeyDown的执⾏流程own的执⾏：和dispatch的流程⼀致，key event从DecorView分发到View的dispatchKeyEvent在chKeyEvent分发到ch:最后分发到own如果own没有返回true，那么key event会继续流传给Activity：最后会传给own总结：own如果返回true，表⽰View消耗了这个事件，那么这个事件不会再流转到Activity3、onKeyUp的执⾏流程onKeyUp的流程和onKeyDown类似，不再累述。总结：p如果返回true，表⽰View消耗了这个事件，那么这个事件不会再流转到Activity。并且onKeyUp的流转和onKeyDown是独⽴的，不会相互影响。