Andorid Touch 事件情景解析

来源：互联网发布：淘宝店铺代装修编辑：程序博客网时间：2024/05/16 12:02

1: 如果所有的子view都没有消费down事件，事件如何传递

测试代码如下

public class ActivityTouchTestActivity extends AppCompatActivity {    private static final String Tag = ActivityTouchTestActivity.class.getSimpleName();    @Bind(R.id.touch_btn)    Button touchBtn;    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        setContentView(R.layout.activity_activity_touch_test);        ButterKnife.bind(this);        Toolbar toolbar = (Toolbar) findViewById(R.id.toolbar);        setSupportActionBar(toolbar);        FloatingActionButton fab = (FloatingActionButton) findViewById(R.id.fab);        fab.setOnClickListener(new View.OnClickListener() {            @Override            public void onClick(View view) {                Snackbar.make(view, "Replace with your own action", Snackbar.LENGTH_LONG)                        .setAction("Action", null).show();            }        });        touchBtn.setOnTouchListener(new View.OnTouchListener() {            @Override            public boolean onTouch(View v, MotionEvent event) {                return false;            }        });    }    @Override    public boolean dispatchTouchEvent(MotionEvent ev) {        boolean result=super.dispatchTouchEvent(ev);        Log.v(Tag , "cong " + result);        return  result;    }}

/** * Created by qing on 16/6/14. */public class BtnTouchView extends Button {    private static final String Tag = BtnTouchView.class.getSimpleName();    public BtnTouchView(Context context, AttributeSet attrs) {        super(context, attrs);    }    @Override    public boolean dispatchTouchEvent(MotionEvent ev) {        boolean result=super.dispatchTouchEvent(ev);        Log.v(Tag, "cong " + result);        return  false;    }}

log如下：

结论：1 : touch事件传回activity的dispatchTouchEvent，而activity的dispatchTouchEvent并不会将值置为true

2: up事件并未传导到btn

分析：

viewGroup的dispatchTouchEvent中有这么一段代码

            if (actionMasked == MotionEvent.ACTION_DOWN                    || mFirstTouchTarget != null) {                final boolean disallowIntercept = (mGroupFlags & FLAG_DISALLOW_INTERCEPT) != 0;                if (!disallowIntercept) {                    intercepted = onInterceptTouchEvent(ev);                    ev.setAction(action); // restore action in case it was changed                } else {                    intercepted = false;                }            } else {                // There are no touch targets and this action is not an initial down                // so this view group continues to intercept touches.                intercepted = true;            }

mFirstTouchTarget只有在事件被消费后才会置值，而实际中btn并未消费事件，所以为null，所以viewGroup本身会拦截事件（up事件由viewgroup本身处理）！！！

结果会直行到dispatchTouchEvent中的这块代码：

   // Dispatch to touch targets.            if (mFirstTouchTarget == null) {                // No touch targets so treat this as an ordinary view.                handled = dispatchTransformedTouchEvent(ev, canceled, null,                        TouchTarget.ALL_POINTER_IDS);

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