android 控件跟隨手指移動

項目中遇到控件跟隨手指觸摸移動的部分，簡單測試了下。

[java] view plain copy

package com.example.viewanimationtest;

/**
 * @author maria
 * 2013-2-16
 */
import android.os.Bundle;
import android.app.Activity;
import android.view.MotionEvent;
import android.view.View;
import android.view.View.OnTouchListener;
import android.view.ViewGroup;
import android.widget.Button;
import android.widget.RelativeLayout;

public class MainActivity extends Activity implements OnTouchListener {

    Button _view;
    ViewGroup _root;
    private int _xDelta;
    private int _yDelta;

    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        _root = (ViewGroup) findViewById(R.id.root);

        _view = (Button) findViewById(R.id.id_text);

        RelativeLayout.LayoutParams layoutParams = new RelativeLayout.LayoutParams(
                150, 50);
        layoutParams.leftMargin = 50;
        layoutParams.topMargin = 50;
        layoutParams.bottomMargin = -250;
        layoutParams.rightMargin = -250;
        _view.setLayoutParams(layoutParams);
        _view.setOnTouchListener(this);
    }

    public boolean onTouch(View view, MotionEvent event) {
        final int X = (int) event.getRawX();
        final int Y = (int) event.getRawY();
        switch (event.getAction() & MotionEvent.ACTION_MASK) {
        case MotionEvent.ACTION_DOWN:
            RelativeLayout.LayoutParams lParams = (RelativeLayout.LayoutParams) view
                    .getLayoutParams();
            _xDelta = X - lParams.leftMargin;
            _yDelta = Y - lParams.topMargin;
            break;
        case MotionEvent.ACTION_UP:
            break;
        case MotionEvent.ACTION_POINTER_DOWN:
            break;
        case MotionEvent.ACTION_POINTER_UP:
            break;
        case MotionEvent.ACTION_MOVE:
            RelativeLayout.LayoutParams layoutParams = (RelativeLayout.LayoutParams) view
                    .getLayoutParams();
            layoutParams.leftMargin = X - _xDelta;
            layoutParams.topMargin = Y - _yDelta;
            layoutParams.rightMargin = -250;
            layoutParams.bottomMargin = -250;
            view.setLayoutParams(layoutParams);
            break;
        }
        _root.invalidate();
        return true;
    }
}

 

.xml

[html] view plain copy

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:id="@+id/root"
    tools:context=".MainActivity" >

    <Button
        android:id="@+id/id_text"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_centerHorizontal="true"
        android:layout_centerVertical="true"
        android:text="@string/hello_world" />

</RelativeLayout>