实现可拖动的按钮视图

public class DraftTest extends Activity {

@Override

public void onCreate(Bundle savedInstanceState) {

super.onCreate(savedInstanceState);

setContentView(R.layout.main);

DisplayMetrics dm = getResources().getDisplayMetrics();

final int screenWidth = dm.widthPixels;

final int screenHeight = dm.heightPixels - 50;

final Button btn = (Button) findViewById(R.id.btn);

btn.setOnTouchListener(new OnTouchListener() {

int lastX, lastY;

@Override

public boolean onTouch(View v, MotionEvent event) {

int ea = event.getAction();

Log.i(\"TAG\", \"Touch:\" + ea);

switch (ea) {

case MotionEvent.ACTION_DOWN:

lastX = (int) event.getRawX();// 获取触摸事件触摸位置的原始X坐标

lastY = (int) event.getRawY();

break;

case MotionEvent.ACTION_MOVE:

int dx = (int) event.getRawX() - lastX;

int dy = (int) event.getRawY() - lastY;

int l = v.getLeft() + dx;

int b = v.getBottom() + dy;

int r = v.getRight() + dx;

int t = v.getTop() + dy;

// 下面判断移动是否超出屏幕

if (l < 0) {

l = 0;

r = l + v.getWidth();

}

if (t < 0) {

t = 0;

b = t + v.getHeight();

}

if (r > screenWidth) {

r = screenWidth;

l = r - v.getWidth();

}

if (b > screenHeight) {

b = screenHeight;

t = b - v.getHeight();

}

v.layout(l, t, r, b);

lastX = (int) event.getRawX();

lastY = (int) event.getRawY();

Toast.makeText(DraftTest.this,

\"当前位置：\" + l + \",\" + t + \",\" + r + \",\" + b,

Toast.LENGTH_SHORT).show();

v.postInvalidate();

break;

case MotionEvent.ACTION_UP:

break;

}

return false;

}

});

}

}

main.xml

<?xml version=\"1.0\" encoding=\"utf-8\"?>

<LinearLayout xmlns:android=\"http://schemas.android.com/apk/res/android\"

android:orientation=\"vertical\"

android:layout_width=\"fill_parent\"

android:layout_height=\"fill_parent\">

<Button

android:text=\"拖动\"

android:id=\"@+id/btn\"

android:layout_width=\"wrap_content\"

android:layout_height=\"wrap_content\"/>

</LinearLayout>