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我是新來android.now我創建拖放功能使用三個按鈕。我做了檢查拖動按鈕不應該空，因爲我必須從該按鈕獲取數據，並且放下按鈕應該是空的。如何檢查拖放是否爲空或不在android
如何將按鈕移動到只靠近按鈕？如果b1，b2，b3橫向出現，則意味着b1必須移動b2，但是可以移動兩側，而b3只能移動b2一側。我的代碼在這裏。請引導我。
import android.content.ClipData;
import android.graphics.Canvas;
import android.graphics.Point;
import android.graphics.drawable.ColorDrawable;
import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.util.Log;
import android.view.DragEvent;
import android.view.View;
import android.view.View.OnDragListener;
import android.view.View.OnLongClickListener;
import android.widget.Button;
public class MainActivity extends AppCompatActivity {
Button b1,b2,b3;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
b1 = (Button) findViewById(R.id.b1);
b2 = (Button) findViewById(R.id.b2);
b3 = (Button) findViewById(R.id.b3);
findViewById(R.id.b1).setOnLongClickListener(longClickListener);
findViewById(R.id.b2).setOnLongClickListener(longClickListener);
findViewById(R.id.b3).setOnLongClickListener(longClickListener);
findViewById(R.id.b1).setOnDragListener(dragListener);
findViewById(R.id.b2).setOnDragListener(dragListener);
findViewById(R.id.b3).setOnDragListener(dragListener);
}
OnLongClickListener longClickListener = new OnLongClickListener() {
@Override
public boolean onLongClick(View view) {
DragShadow dragShadow = new DragShadow(view);
ClipData clipData = ClipData.newPlainText("","");
view.startDrag(clipData, dragShadow, view, 0);
return true;
}
};
private class DragShadow extends View.DragShadowBuilder{
ColorDrawable greyBox;
public DragShadow(View v){
super(v);
greyBox = new ColorDrawable(R.color.button_material_light);
}
@Override
public void onDrawShadow(Canvas canvas) {
greyBox.draw(canvas);
}
@Override
public void onProvideShadowMetrics(Point shadowSize, Point
shadowTouchPoint) {
View v = getView();
int height = (int) v.getHeight();
int width = (int) v.getWidth();
greyBox.setBounds(0,0,width,height);
shadowSize.set(width,height);
shadowTouchPoint.set((int) width/2,(int) height/2);
}
}
OnDragListener dragListener = new OnDragListener() {
@Override
public boolean onDrag(View view, DragEvent dragEvent) {
int dEvent = dragEvent.getAction();
switch (dEvent) {
case DragEvent.ACTION_DRAG_ENTERED:
Log.i("Drag Event", "Entered");
break;
case DragEvent.ACTION_DRAG_EXITED:
Log.i("Drag Event", "Exited");
break;
case DragEvent.ACTION_DROP:
Button b = (Button) view;
if (b.getText().toString().matches("")) {
Button dragged = (Button) dragEvent.getLocalState();
CharSequence a = b.getText();
b.setText(dragged.getText());
dragged.setText(a);
} else{
Toast.makeText(getApplicationContext(),"inserting button should be empty",Toast.LENGTH_SHORT).show();
}
break;
}
return true;
}
};
}