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我正在爲我的應用程序創建拖放功能，現在我只是通過一個教程來讓我習慣於基本知識。我希望能夠在我的真實設備上運行我的應用程序，但版本不支持4.0及更高版本（因爲拖放使用Gridlayout）。但它支持API 8.Gridlayout支持版本低於4.0
我環顧四周，發現人們使用支持v7 gridlayout來支持較小的版本。我如何實現這個到我的應用程序？我得到的錯誤在我的drag_and_drop_app.xml：
<?xml version="1.0" encoding="utf-8"?>
<GridLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:layout_width="match_parent"
android:layout_height="match_parent"
android:columnCount="2"
android:columnWidth="300dp"
android:orientation="vertical"
android:rowCount="2"
android:stretchMode="columnWidth" >
<LinearLayout
android:id="@+id/topleft"
android:layout_width="160dp"
android:layout_height="200dp"
android:layout_column="0"
android:layout_row="0"
android:background="@drawable/shape" >
<ImageView
android:id="@+id/myimage1"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_column="0"
android:layout_row="0"
android:src="@drawable/ic_launcher" />
</LinearLayout>
<LinearLayout
android:id="@+id/topright"
android:layout_width="160dp"
android:layout_height="200dp"
android:layout_column="1"
android:layout_row="0"
android:background="@drawable/shape" >
<ImageView
android:id="@+id/myimage2"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_column="0"
android:layout_row="0"
android:src="@drawable/ic_launcher" />
</LinearLayout>
<LinearLayout
android:id="@+id/bottomleft"
android:layout_width="160dp"
android:layout_height="200dp"
android:layout_column="0"
android:layout_row="1"
android:background="@drawable/shape" >
<ImageView
android:id="@+id/myimage3"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:src="@drawable/ic_launcher" />
</LinearLayout>
<LinearLayout
android:id="@+id/bottomright"
android:layout_width="160dp"
android:layout_height="200dp"
android:layout_column="1"
android:layout_row="1"
android:background="@drawable/shape" >
<ImageView
android:id="@+id/myimage4"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_column="0"
android:layout_row="0"
android:src="@drawable/ic_launcher" />
</LinearLayout>
</GridLayout>
和Drag_and_Drop_App.java：
package com.example.awesomefilebuilderwidget;
import android.app.Activity;
import android.content.ClipData;
import android.graphics.drawable.Drawable;
import android.os.Bundle;
import android.view.DragEvent;
import android.view.MotionEvent;
import android.view.View;
import android.view.View.DragShadowBuilder;
import android.view.View.OnDragListener;
import android.view.View.OnTouchListener;
import android.view.ViewGroup;
import android.widget.LinearLayout;
public class Drag_and_Drop_App extends Activity {
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.drag_and_drop_app);
findViewById(R.id.myimage1).setOnTouchListener(new MyTouchListener());
findViewById(R.id.myimage2).setOnTouchListener(new MyTouchListener());
findViewById(R.id.myimage3).setOnTouchListener(new MyTouchListener());
findViewById(R.id.myimage4).setOnTouchListener(new MyTouchListener());
findViewById(R.id.topleft).setOnDragListener(new MyDragListener());
findViewById(R.id.topright).setOnDragListener(new MyDragListener());
findViewById(R.id.bottomleft).setOnDragListener(new MyDragListener());
findViewById(R.id.bottomright).setOnDragListener(new MyDragListener());
}
private final class MyTouchListener implements OnTouchListener {
public boolean onTouch(View view, MotionEvent motionEvent) {
if (motionEvent.getAction() == MotionEvent.ACTION_DOWN) {
ClipData data = ClipData.newPlainText("", "");
DragShadowBuilder shadowBuilder = new View.DragShadowBuilder(view);
view.startDrag(data, shadowBuilder, view, 0);
view.setVisibility(View.INVISIBLE);
return true;
} else {
return false;
}
}
}
class MyDragListener implements OnDragListener {
Drawable enterShape = getResources().getDrawable(R.drawable.shape_droptarget);
Drawable normalShape = getResources().getDrawable(R.drawable.shape);
@Override
public boolean onDrag(View v, DragEvent event) {
int action = event.getAction();
switch (event.getAction()) {
case DragEvent.ACTION_DRAG_STARTED:
// do nothing
break;
case DragEvent.ACTION_DRAG_ENTERED:
v.setBackgroundDrawable(enterShape);
break;
case DragEvent.ACTION_DRAG_EXITED:
v.setBackgroundDrawable(normalShape);
break;
case DragEvent.ACTION_DROP:
// Dropped, reassign View to ViewGroup
View view = (View) event.getLocalState();
ViewGroup owner = (ViewGroup) view.getParent();
owner.removeView(view);
LinearLayout container = (LinearLayout) v;
container.addView(view);
view.setVisibility(View.VISIBLE);
break;
case DragEvent.ACTION_DRAG_ENDED:
v.setBackgroundDrawable(normalShape);
default:
break;
}
return true;
}
}
}