无法在android studio中拖放一个简单的imageView

Question

我正在尝试在android studio中创建一个简单的拖放图像.我可以让图像在屏幕上拖动,一旦我释放它就会消失.在控制台中,我收到"报告丢弃结果:false"

这是我的代码:

ImageView mImageView;
String mString;

private android.widget.RelativeLayout.LayoutParams mLayoutParams;

    mImageView.setOnLongClickListener(new View.OnLongClickListener(){
        @Override
        public boolean onLongClick(View v){
            ClipData.Item item = new ClipData.Item((CharSequence)v.getTag());
            String[] mimeTypes = {
                    ClipDescription.MIMETYPE_TEXT_PLAIN
            };
            ClipData dragData = new ClipData(v.getTag().toString(), mimeTypes, item);
            View.DragShadowBuilder myShadow = new View.DragShadowBuilder(mImageView);

            v.startDrag(dragData, myShadow, null, 0);
            return true;
        }
    });

    mImageView.setOnDragListener(new View.OnDragListener() {
        @Override
        public boolean onDrag(View v, DragEvent event) {
            switch(event.getAction()) {
                case DragEvent.ACTION_DRAG_STARTED:
                    mLayoutParams = (RelativeLayout.LayoutParams)v.getLayoutParams();
                    Log.d(mString, "Action is DragEvent.ACTION_DRAG_STARTED");

                    // Do nothing
                    break;

                case DragEvent.ACTION_DRAG_ENTERED:
                    Log.d(mString, "Action is DragEvent.ACTION_DRAG_ENTERED");
                    int x_cord = (int) event.getX();
                    int y_cord = (int) event.getY();
                    break;

                case DragEvent.ACTION_DRAG_EXITED :
                    Log.d(mString, "Action is DragEvent.ACTION_DRAG_EXITED");
                    x_cord = (int) event.getX();
                    y_cord = (int) event.getY();
                    mLayoutParams.leftMargin = x_cord;
                    mLayoutParams.topMargin = y_cord;
                    v.setLayoutParams(mLayoutParams);
                    break;

                case DragEvent.ACTION_DRAG_LOCATION  :
                    Log.d(mString, "Action is DragEvent.ACTION_DRAG_LOCATION");
                    x_cord = (int) event.getX();
                    y_cord = (int) event.getY();
                    break;

                case DragEvent.ACTION_DRAG_ENDED   :
                    Log.d(mString, "Action is DragEvent.ACTION_DRAG_ENDED");

                    // Do nothing
                    break;

                case DragEvent.ACTION_DROP:
                    Log.d(mString, "ACTION_DROP event");

                    // Do nothing
                    break;
                default: break;
            }
            return true;
        }
    });

    mImageView.setOnTouchListener(new View.OnTouchListener(){
        @Override
        public boolean onTouch(View v, MotionEvent event) {
            if (event.getAction() == MotionEvent.ACTION_DOWN) {
                ClipData data = ClipData.newPlainText("", "");
                View.DragShadowBuilder shadowBuilder = new View.DragShadowBuilder(mImageView);

                mImageView.startDrag(data, shadowBuilder, mImageView, 0);
                mImageView.setVisibility(View.INVISIBLE);
                return true;
            } else {
                return false;
            }
        }
    });
}

}

Answer 1

编辑:更改了一个如何使用onTouch移动RelativeLayout中包含的所有视图的工作示例.我认为onDrag事件更适用于拖放数据项,而不是移动视图.

public class MainActivity extends AppCompatActivity implements View.OnTouchListener {
    private RelativeLayout mRelLay;
    private float mInitialX, mInitialY;
    private int mInitialLeft, mInitialTop;
    private View mMovingView = null;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        mRelLay = (RelativeLayout) findViewById(R.id.relativeLayout);

        for (int i = 0; i < mRelLay.getChildCount(); i++)
            mRelLay.getChildAt(i).setOnTouchListener(this);
    }

    @Override
    public boolean onTouch(View view, MotionEvent motionEvent) {
        RelativeLayout.LayoutParams mLayoutParams;

        switch (motionEvent.getAction()) {
            case MotionEvent.ACTION_DOWN:
                mMovingView = view;
                mLayoutParams = (RelativeLayout.LayoutParams) mMovingView.getLayoutParams();
                mInitialX = motionEvent.getRawX();
                mInitialY = motionEvent.getRawY();
                mInitialLeft = mLayoutParams.leftMargin;
                mInitialTop = mLayoutParams.topMargin;
                break;

            case MotionEvent.ACTION_MOVE:
                if (mMovingView != null) {
                    mLayoutParams = (RelativeLayout.LayoutParams) mMovingView.getLayoutParams();
                    mLayoutParams.leftMargin = (int) (mInitialLeft + motionEvent.getRawX() - mInitialX);
                    mLayoutParams.topMargin = (int) (mInitialTop + motionEvent.getRawY() - mInitialY);
                    mMovingView.setLayoutParams(mLayoutParams);
                }
                break;

            case MotionEvent.ACTION_UP:
                mMovingView = null;
                break;
        }

        return true;
    }
}

Answer 2

给出的代码有一个问题很容易解决.的OnDragListener()应为目的地(或任何可能的目的地)图来设定.所以OnLongClickListener()和OnTouchListener()在源视图设置,imageView那么就应该imageView2为OnDragListener().这是一个很长的解释,但应该是一个简单的解决方案.

请参阅拖放示例.

如果正确完成,其余的解决方案将更加复杂(但是,有一个解决方法).

开始拖动时,基本上您需要将图像复制到剪贴板,然后将其粘贴到拖放视图中.这需要创建一个ContentProvider然后使用ContentResolver(链接).

剪贴板文档:ClipData

我有未来计划为应用程序执行此操作,但这不会很快发生,所以,不幸的是,我将无法提供任何代码.

但是,有一种解决方法更少涉及.

在可能被移动的任何图像上设置标记.

imageView.setTag("ImageTag1");

在onLongClick(),设置item和dragData在问题中完成.

然后OnDragListener(),读取标签,确定要删除的图像,然后将该图像设置为视图.像这样的东西:

case DragEvent.ACTION_DROP:
    ClipData.Item item = event.getClipData().getItemAt(0);
    CharSequence dragData = item.getText();

    if(dragData.equals("ImageTag1")) {
        // this gets jpg image from "drawable" folder,
        //      set ImageView appropriately for your usage
        ((ImageView)v).setImageResource(R.drawable.image1);                            
    } else if(dragData.equals("ImageTag2")) {
        ((ImageView)v).setImageResource(R.drawable.image2);
    }
    break;

在"ACTION_DRAG_EXITED"的情况下,您还需要执行类似的操作.如果将图像放在无效区域中,则会将图像放回原始视图.