版本:1.0
日期:2014.4.29
版权:© 2014 kince 转载注明出处
关于View的拖动大家应该比较了解了,比如对一个控件IamgeView拖动,或者一个视图View拖动,实现方式也很容易,继承OnTouchListener接口,然后重写onTouch方法,在触屏事件进行处理即可。但是Popupwindow如何实现拖动呢,我们都知道它和普通的View不一样,因为它不是继承于View类的,但是它的实现却是和View密切相关的,因为我们都知道Android视图的显示都是由View来处理的,所以一定离不开它。从Popupwindow的实现就可以看出来,
import com.android.internal.R;
import android.content.Context;
import android.content.res.Resources;
import android.content.res.TypedArray;
import android.graphics.PixelFormat;
import android.graphics.Rect;
import android.graphics.drawable.Drawable;
import android.graphics.drawable.StateListDrawable;
import android.os.Build;
import android.os.IBinder;
import android.util.AttributeSet;
import android.view.Gravity;
import android.view.KeyEvent;
import android.view.MotionEvent;
import android.view.View;
import android.view.View.OnTouchListener;
import android.view.ViewGroup;
import android.view.ViewTreeObserver;
import android.view.ViewTreeObserver.OnScrollChangedListener;
import android.view.WindowManager;
import java.lang.ref.WeakReference;
上面是它的导包情况,基本上不是和View相关,就是和绘图相关。因此关于Popupwindow的拖动这一块,也和View有联系。首先看一下它的API,看一看有没有和View移动、变化相关的方法,果然在最后有几个update()方法,如下:
update()方法用来更新Popupwindow的位置和大小的,那么问题就好解决了。看代码:
package com.example.drag_and_drop_movablepopupwindow;
import android.support.v7.app.ActionBarActivity;
import android.graphics.Color;
import android.os.Bundle;
import android.view.Gravity;
import android.view.LayoutInflater;
import android.view.Menu;
import android.view.MenuItem;
import android.view.MotionEvent;
import android.view.View;
import android.view.View.OnTouchListener;
import android.view.ViewGroup.LayoutParams;
import android.widget.Button;
import android.widget.PopupWindow;
import android.widget.TextView;
public class MainActivity extends ActionBarActivity {
private Button btnOpenPopup;
private int mCurrentX;
private int mCurrentY;
private PopupWindow mPopup;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
btnOpenPopup = (Button) findViewById(R.id.openpopup);
btnOpenPopup.setOnClickListener(new Button.OnClickListener() {
@Override
public void onClick(View arg0) {
creatPopubWindow_1();
}
});
}
/**
* 1
*/
private void creatPopubWindow_1() {
LayoutInflater layoutInflater = (LayoutInflater) getBaseContext()
.getSystemService(LAYOUT_INFLATER_SERVICE);
View popupView = layoutInflater.inflate(R.layout.popup, null);
final PopupWindow popupWindow = new PopupWindow(popupView,
200, 200);
Button btnDismiss = (Button) popupView.findViewById(R.id.dismiss);
btnDismiss.setOnClickListener(new Button.OnClickListener() {
@Override
public void onClick(View v) {
popupWindow.dismiss();
}
});
popupWindow.showAsDropDown(btnOpenPopup, 50, 50);
popupView.setOnTouchListener(new OnTouchListener() {
int orgX, orgY;
int offsetX, offsetY;
@Override
public boolean onTouch(View v, MotionEvent event) {
switch (event.getAction()) {
case MotionEvent.ACTION_DOWN:
orgX = (int) event.getX();
orgY = (int) event.getY();
break;
case MotionEvent.ACTION_MOVE:
offsetX = (int) event.getRawX() - orgX;
offsetY = (int) event.getRawY() - orgY;
popupWindow.update(offsetX, offsetY, -1, -1, true);
break;
}
return true;
}
});
}
}
效果如图:
首先对Popupwindow设置触摸事件,然后在回调方法中进行计算,如果手指拖动了Popupwindow,那么就调用update()方法来更新它的位置。有些同学可能不太理解参数-1是什么意思,在上面的API中,写明的是宽和高,这里怎么变成-1了呢,看一下Popupwindow源代码就明白了。
/**
* Updates the position and the dimension of the popup window. Width and
* height can be set to -1 to update location only. Calling this function
* also updates the window with the current popup state as
* described for {@link #update()}.
*
* @param x the new x location
* @param y the new y location
* @param width the new width, can be -1 to ignore
* @param height the new height, can be -1 to ignore
* @param force reposition the window even if the specified position
* already seems to correspond to the LayoutParams
*/
public void update(int x, int y, int width, int height, boolean force) {
if (width != -1) {
mLastWidth = width;
setWidth(width);
}
if (height != -1) {
mLastHeight = height;
setHeight(height);
}
if (!isShowing() || mContentView == null) {
return;
}
WindowManager.LayoutParams p = (WindowManager.LayoutParams) mPopupView.getLayoutParams();
boolean update = force;
final int finalWidth = mWidthMode < 0 ? mWidthMode : mLastWidth;
if (width != -1 && p.width != finalWidth) {
p.width = mLastWidth = finalWidth;
update = true;
}
final int finalHeight = mHeightMode < 0 ? mHeightMode : mLastHeight;
if (height != -1 && p.height != finalHeight) {
p.height = mLastHeight = finalHeight;
update = true;
}
if (p.x != x) {
p.x = x;
update = true;
}
if (p.y != y) {
p.y = y;
update = true;
}
final int newAnim = computeAnimationResource();
if (newAnim != p.windowAnimations) {
p.windowAnimations = newAnim;
update = true;
}
final int newFlags = computeFlags(p.flags);
if (newFlags != p.flags) {
p.flags = newFlags;
update = true;
}
if (update) {
setLayoutDirectionFromAnchor();
mWindowManager.updateViewLayout(mPopupView, p);
}
}
前两个if判断已经说得很清楚了,如果参数是-1的话,就不改变Popupwindow的大小了,因为我们只是移动位置,所以才这样写。那关于Popupwindow的移动最后是怎么实现的呢,可以看出就是调用WindowManager的updateViewLayout()方法,这个方法在WindowManager中并没有实现,它是ViewManager接口里面的方法,WindowManager继承了ViewManager。说到ViewManager,它里面定义的方法都很常用,看代码:
/** Interface to let you add and remove child views to an Activity. To get an instance
* of this class, call {@link android.content.Context#getSystemService(java.lang.String) Context.getSystemService()}.
*/
public interface ViewManager
{
/**
* Assign the passed LayoutParams to the passed View and add the view to the window.
* Throws {@link android.view.WindowManager.BadTokenException} for certain programming
* errors, such as adding a second view to a window without removing the first view.
*
Throws {@link android.view.WindowManager.InvalidDisplayException} if the window is on a
* secondary {@link Display} and the specified display can't be found
* (see {@link android.app.Presentation}).
* @param view The view to be added to this window.
* @param params The LayoutParams to assign to view.
*/
public void addView(View view, ViewGroup.LayoutParams params);
public void updateViewLayout(View view, ViewGroup.LayoutParams params);
public void removeView(View view);
}
这下大家应该明了,我们经常用的addView、removeView方法就是在这里面定义的,那么谁去实现呢?就是Layout控件,比如LinearLayout、RelativeLayout等,所以我们刚才用的updateViewLayout()方法也是在xml布局文件中的layout定义好的。