android: how can I detect when user touch left 20% of view area?

问题

In an activity by using

public boolean dispatchTouchEvent(MotionEvent ev)

how can I know an user is touching left Y-axis of 20% edge area?

It should be generic and orientation handled. I don't want to create any hidden view on that.

回答1:

• Get device width
• Calculate left 20% width size (from 0 to X)
• Use event.getX()
• Check that event.getX() is inside device with 20%

example :

public class YourActivity extends Activity {

        private LinearLayout background;
        private float xValue, yValue, leftPersentage;
        private int height,width;


        @Override
        protected void onCreate(Bundle savedInstanceState) {
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_home);

            DisplayMetrics displaymetrics = new DisplayMetrics();
            getWindowManager().getDefaultDisplay().getMetrics(displaymetrics);
            height = displaymetrics.heightPixels;
            width = displaymetrics.widthPixels;

            leftPersentage = (width)*20/100;

            background = (LinearLayout) findViewById(R.id.background);
            background.setOnTouchListener(new View.OnTouchListener() {
                @Override
                public boolean onTouch(View v, MotionEvent event) {
                    xValue = event.getX();
                    yValue = event.getY();
                    Log.d("Values Clicked" , xValue +"and" + yValue);
                    if(xValue <= leftPersentage){
                        // perform your task 
                        Log.d("Values Clicked onLeft" , xValue +"and" + yValue);
                    }

                    return false;
                }
            });
        }
    }

回答2:

Get the display size then get the point from touch event. Compare it mathematically to know if its left 20% or not.

get display size

DisplayMetrics displayMetrics = context.getResources().getDisplayMetrics();    
float dpHeight = displayMetrics.heightPixels / displayMetrics.density;
float dpWidth = displayMetrics.widthPixels / displayMetrics.density;

get the touch points.

@Override
public boolean dispatchTouchEvent(MotionEvent ev) {
    float touchedX = ev.getX();
    float touchedY = ev.getY();
    return super.dispatchTouchEvent(ev);
}

来源：https://stackoverflow.com/questions/41993859/android-how-can-i-detect-when-user-touch-left-20-of-view-area