[英]Android beginner - Place Image at DragEvent
我意识到已经发布了类似的问题,我已经查看了它们以及许多其他主题等以找到解决方案 - 我显然错过了明显的 - 因为我仍在学习基础知识!
目标:简单的拖放。 用户在屏幕上移动图像,并在另一个图像的顶部或屏幕上的任何位置下降。
API:> 11
已完成:
不工作:
我尝试了很多不同的方法,但总是编译错误。 查看我的代码,任何人都可以推荐一种干净简单的方法将图像放在ACTION_DRAG_ENDED(请记住我是初学者)
这是我的java代码:
public class MainActivity extends Activity {
@Override
public boolean onCreateOptionsMenu(Menu menu) {
// Inflate the menu; this adds items to the action bar if it is present.
getMenuInflater().inflate(R.menu.activity_main, menu);
return true;
}
boolean okToDrop;
/** Called when the activity is first created. */
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
findViewById(R.id.oval).setOnTouchListener(new theTouchListener());
findViewById(R.id.square).setOnTouchListener(new theTouchListener());
findViewById(R.id.robot).setOnTouchListener(new theTouchListener());
findViewById(R.id.oval).setOnDragListener(new theDragListener());
findViewById(R.id.square).setOnDragListener(new theDragListener());
findViewById(R.id.robot).setOnDragListener(new theDragListener());
}
private final class theTouchListener 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.VISIBLE);
return true;
} else {
return false;
}
}
}
class theDragListener implements OnDragListener {
@Override
public boolean onDrag(View view, DragEvent dragEvent) {
int dragAction = dragEvent.getAction();
View dragView = (View) dragEvent.getLocalState();
if (dragAction == DragEvent.ACTION_DRAG_EXITED) {
okToDrop = false;
} else if (dragAction == DragEvent.ACTION_DRAG_ENTERED) {
okToDrop = true;
} else if (dragAction == DragEvent.ACTION_DRAG_ENDED) {
if (dropEventNotHandled(dragEvent) == true) {
// Code to generate image goes here ***********************
Context context = getApplicationContext();
CharSequence text = "Action Dropped Not In Box!";
int duration = Toast.LENGTH_SHORT;
Toast toast = Toast.makeText(context, text, duration);
toast.show();
dragView.setVisibility(View.VISIBLE);
}
} else if (dragAction == DragEvent.ACTION_DROP && okToDrop) {
ImageView i = (ImageView) findViewById(R.id.square);
i.setImageResource(R.drawable.oval);
dragView.setVisibility(View.INVISIBLE);
Context context = getApplicationContext();
CharSequence text = "Action Resulted In It Being Dropped In The Box";
int duration = Toast.LENGTH_SHORT;
Toast toast = Toast.makeText(context, text, duration);
toast.show();
}
return true;
}
private boolean dropEventNotHandled(DragEvent dragEvent) {
return !dragEvent.getResult();
}
}
而我的xml:
<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"
tools:context=".MainActivity" >
<ImageView
android:id="@+id/square"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentRight="true"
android:layout_centerVertical="true"
android:src="@drawable/square_box" />
<ImageView
android:id="@+id/oval"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignParentLeft="true"
android:layout_alignParentTop="true"
android:layout_marginLeft="58dp"
android:layout_marginTop="58dp"
android:src="@drawable/oval" />
<ImageView
android:id="@+id/robot"
android:layout_width="wrap_content"
android:layout_height="wrap_content"
android:layout_alignLeft="@+id/oval"
android:layout_below="@+id/square"
android:layout_marginTop="70dp"
android:src="@drawable/ic_launcher" />
</RelativeLayout>
虽然我不确定我的实现是否是最好的方法,但它确实有效。
在MainActivity中添加这些成员:
View root; // references root activity view
float dropX, dropY; // records position of where finger was lifted on the root
在你的onCreate()中:
root = findViewById(android.R.id.content); // get reference to root
// add a Draglistener to your root view
root.setOnDragListener(new OnDragListener() {
@Override
public boolean onDrag(View v, DragEvent event) {
int action = event.getAction();
if(action == DragEvent.ACTION_DROP) {
// record position of finger lift
dropX = event.getX();
dropY = event.getY();
}
return false;
}
});
最后,将这些行放在// Code to generate image goes here
:
dragView.setX(dropX - dragView.getWidth() / 2);
dragView.setY(dropY - dragView.getHeight() / 2);
希望这可以帮助。
好! 所以你的问题不是使用相同的拖拽监听器。
findViewById(R.id.oval).setOnDragListener(new theDragListener());
应该
theDragListener draglistener = new theDragListener();
findViewById(R.id.oval).setOnDragListener(draglistener);
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