android拖放ImageView onTouchListener

android drag and drop ImageView onTouchListener

提问by Paul Alexander

Hello
I've set up an onTouchListener within my application for an ImageView, my aim was to have an ImageView that the user would be able to drag around and place where ever they want within the app.

I've written some code using sample code found on the web for an onTouchListener that I thought would work but I'm having some problems with it, rather than allowing me to drag the image around, the image resizes and gets bigger or smaller when you drag your finger over it.

Does anyone have any ideas why?
Here's my code:

你好，
我在我的应用程序中为 ImageView 设置了一个 onTouchListener，我的目标是拥有一个 ImageView，用户可以在应用程序中拖动并放置他们想要的任何位置。

我已经使用在网上找到的示例代码编写了一些代码，用于我认为可以工作的 onTouchListener，但我遇到了一些问题，而不是允许我拖动图像，图像会调整大小并变大或变小你将手指拖过它。

有谁知道为什么？
这是我的代码：

    ImageView t1img;

    t1img = (ImageView) findViewById(R.id.imgT1);

    windowWidth = getWindowManager().getDefaultDisplay().getWidth();
    windowHeight = getWindowManager().getDefaultDisplay().getHeight();

    t1img.setOnTouchListener(new View.OnTouchListener() {

        @Override
        public boolean onTouch(View v, MotionEvent event) {

            layoutParams = (LayoutParams) t1img.getLayoutParams();

            switch (event.getAction()) {

                case MotionEvent.ACTION_DOWN:

                break;

                case MotionEvent.ACTION_MOVE:

                    int xCoord = (int) event.getRawX();
                    int yCoord = (int) event.getRawY();

                    if (xCoord > windowWidth) {

                        xCoord = windowWidth;
                    }

                    if (yCoord > windowHeight) {

                        yCoord = windowHeight;
                    }

                    layoutParams.leftMargin = xCoord - 25;
                    layoutParams.topMargin = yCoord - 75;

                    t1img.setLayoutParams(layoutParams);

                break;

                default:

                break;
            }

            return true;
        }
    });

回答by Niko Adrianus Yuwono

If you need to support gingerbread you can take a look at my example here

如果您需要支持姜饼，您可以在这里查看我的示例

https://github.com/NAYOSO/android-dragview

https://github.com/NAYOSO/android-dragview

if you only need to support jelly bean above you can use the Drag and Drop from android library you can see it from this article

如果你只需要支持上面的 jelly bean 你可以使用从 android 库中拖放你可以从这篇文章中看到它

http://developer.android.com/guide/topics/ui/drag-drop.html

http://developer.android.com/guide/topics/ui/drag-drop.html

For some explanation about the Drag and Drop view at first you need t create the touch listener and then call startDrag to start draging. As simple as that.

有关拖放视图的一些说明，首先您不需要创建触摸侦听器，然后调用 startDrag 开始拖动。就如此容易。

private final class dragTouchListener implements OnTouchListener {

        @Override
        public boolean onTouch(View v, MotionEvent event) {
            if (event.getAction() == MotionEvent.ACTION_DOWN) {
                DragShadowBuilder shadowBuilder = new View.DragShadowBuilder(v);
                v.startDrag(data, shadowBuilder, v, 0);
                return true;
            } else {
                return false;
            }
        }

    }

To monitor the target of dropping place you can use onDragListener

要监视放置位置的目标，您可以使用 onDragListener

private class dropListener implements OnDragListener {

    View draggedView;
    CustomTextView dropped;

    @Override
    public boolean onDrag(View v, DragEvent event) {
        switch (event.getAction()) {
        case DragEvent.ACTION_DRAG_STARTED:
            draggedView = (View) event.getLocalState();
            dropped = (CustomTextView) draggedView;
            draggedView.setVisibility(View.INVISIBLE);
            break;
        case DragEvent.ACTION_DRAG_ENTERED:
            break;
        case DragEvent.ACTION_DRAG_EXITED:
            break;
        case DragEvent.ACTION_DROP:

            CustomTextView dropTarget = (CustomTextView) v;
            dropTarget.setText(dropped.getText().toString());
            break;
        case DragEvent.ACTION_DRAG_ENDED:
            break;
        default:
            break;
        }
        return true;
    }

}

As you can see from my code there is many event but the main one is when the view is start being dragged, dropped and ended.

正如您从我的代码中看到的，有很多事件，但主要的事件是在视图开始被拖放和结束时。

Don't forget to set the listener to view

不要忘记设置监听器来查看

    tvDrag.setOnTouchListener(new dragTouchListener());
    tvDrop.setOnDragListener(new dropListener())

I hope my explanation is clear enough! If you have further question I will try to answer it tonight or tomorrow :)

我希望我的解释足够清楚！如果您还有其他问题，我将在今晚或明天尝试回答:)

回答by Daniel Nyamasyo

I have done an example using thread. You can try this example for a smooth drag and drop bitmap image using touch Event listener

我用线程做了一个例子。您可以尝试使用触摸事件侦听器平滑拖放位图图像的此示例

Download Demo or Code

下载演示或代码

I have created three classes MainActivity.Java Instatiates our BallView class and Adds setContentView to the BallView Class as shown below

我创建了三个类 MainActivity.Java 实例化我们的 BallView 类并将 setContentView 添加到 BallView 类，如下所示

package com.whatsonline.dragobject;

import android.app.Activity;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.os.Bundle;

public class MainActivity extends Activity {

    private Bitmap bitmap;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        int w=getWindowManager().getDefaultDisplay().getWidth()-25;
        int h=getWindowManager().getDefaultDisplay().getHeight()-25;
        bitmap = BitmapFactory.decodeResource(getResources(), R.drawable.p1);
        BallView ballView=new BallView(this, bitmap, w, h);
        setContentView(ballView);
    }

}

Our BallView extends the surfaceView class and implements the surface holder as shown below. Also, contains the draw method to draw the canvas and touchEvent listener to get the position of the Bitmap image to be moved and move along the drawn image Bitmap path.

我们的 BallView 扩展了 surfaceView 类并实现了如下所示的表面保持器。此外，包含绘制画布的 draw 方法和获取要移动的 Bitmap 图像的位置以及沿绘制的图像 Bitmap 路径移动的 touchEvent 侦听器。

package com.whatsonline.dragobject;

import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;
import android.graphics.Color;
import android.view.MotionEvent;
import android.view.SurfaceHolder;
import android.view.SurfaceView;


public class BallView extends SurfaceView implements SurfaceHolder.Callback {

    private Bitmap bitmap;
    private MyThread thread;
    private int x=25,y=25;
    int width,height;

    public BallView(Context context, Bitmap bmp, int w,int h) {
        super(context);

        width=w;
        height=h;
        bitmap=bmp;
        thread=new MyThread(getHolder(),this);
        getHolder().addCallback(this);
        setFocusable(true);
    }

    @Override
    public void onDraw(Canvas canvas) {
        super.onDraw(canvas);

       // bitmap = BitmapFactory.decodeResource(getResources(), bmp);
        canvas.drawColor(Color.BLUE);//To make background
        canvas.drawBitmap(bitmap, x-(bitmap.getWidth()/2),y-(bitmap.getHeight()/2), null);


    }

    @Override
    public boolean onTouchEvent(MotionEvent event) {

        x=(int)event.getX();
        y=(int)event.getY();

        if(x<25)
            x=25;
        if(x> width)
            x=width;
        if(y <25)
            y=25;
        if(y > height)
            y=height;

        return true;
    }

    @Override
    public void surfaceChanged(SurfaceHolder holder, int format, int width,int height) {
        // TODO Auto-generated method stub

    }

    @Override
    public void surfaceCreated(SurfaceHolder holder) {

        thread.startrun(true);
        thread.start();

    }

    @Override
    public void surfaceDestroyed(SurfaceHolder holder) {


        thread.startrun(false);
        thread.stop();

    }
}

and finally MainThread class call the onDraw method if it is running as shown below

最后 MainThread 类调用 onDraw 方法，如果它正在运行，如下所示

package com.whatsonline.dragobject;

import android.graphics.Canvas;
import android.view.SurfaceHolder;

public class MyThread extends Thread {

    private SurfaceHolder msurfaceHolder;
    private BallView mballView;
    private boolean mrun =false;

    public MyThread(SurfaceHolder holder, BallView ballView) {

        msurfaceHolder = holder;
        mballView=ballView;
    }

    public void startrun(boolean run) {

        mrun=run;
    }

    @Override
    public void run() {

        super.run();
        Canvas canvas;
        while (mrun) {
            canvas=null;
            try {
                canvas = msurfaceHolder.lockCanvas(null);
                synchronized (msurfaceHolder) {
                    mballView.onDraw(canvas);
                }
            } finally {
                if (canvas != null) {
                    msurfaceHolder.unlockCanvasAndPost(canvas);
                }
            }
        }
    }

}

Download code here

在这里下载代码