android - 图像拖放

Question

我已经开始了上一题，但是我想改变拖动的方式。

所以任务是，用户( child )学习如何做加法。所以有 2 颗糖果和 1 个糖果 jar 。用户需要将糖果拖放到 jar 里。怎么做？

这些是我的代码:

主要 xml

<?xml version="1.0" encoding="utf-8"?>


<AbsoluteLayout android:layout_width="fill_parent" android:layout_height="fill_parent" xmlns:android="http://schemas.android.com/apk/res/android" android:id="@+id/mainLayout">
<ImageView android:layout_height="wrap_content" android:layout_width="wrap_content" android:id="@+id/emptyLetterView" android:src="@drawable/r_empty" android:layout_x="200px" android:layout_y="300px"></ImageView>
<ImageView android:layout_height="wrap_content" android:layout_width="wrap_content" android:id="@+id/letterView" android:src="@drawable/r_filled" ></ImageView>
</AbsoluteLayout>

这是java文件 包 edu.sbcc.cs123.draganddropbasic;

import android.app.*;
import android.graphics.*;
import android.os.*;
import android.view.*;
import android.view.View.*;
import android.widget.*;

@SuppressWarnings("deprecation")
public class DragAndDropBasicActivity extends Activity implements OnTouchListener {
    private ImageView letterView;                       // The letter that the user drags.
    private ImageView emptyLetterView;              // The letter outline that the user is supposed to drag letterView to.
    private AbsoluteLayout mainLayout;


    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        mainLayout = (AbsoluteLayout) findViewById(R.id.mainLayout);
        mainLayout.setOnTouchListener(this);
        letterView = (ImageView) findViewById(R.id.letterView);
        letterView.setOnTouchListener(this);

        emptyLetterView = (ImageView) findViewById(R.id.emptyLetterView);
    }

    private boolean dragging = false;
    private Rect hitRect = new Rect();

    @Override
    /**
     * NOTE:  Had significant problems when I tried to react to ACTION_MOVE on letterView.   Kept getting alternating (X,Y) 
     * locations of the motion events, which caused the letter to flicker and move back and forth.  The only solution I could 
     * find was to determine when the user had touched down on the letter, then process moves in the ACTION_MOVE 
     * associated with the mainLayout.
     */
    public boolean onTouch(View v, MotionEvent event) {
        boolean eventConsumed = true;
        int x = (int)event.getX();
        int y = (int)event.getY();

        int action = event.getAction();
        if (action == MotionEvent.ACTION_DOWN) {
            if (v == letterView) {
                dragging = true;
                eventConsumed = false;
            }
        } else if (action == MotionEvent.ACTION_UP) {

            if (dragging) {
                emptyLetterView.getHitRect(hitRect);
                if (hitRect.contains(x, y))
                    setSameAbsoluteLocation(letterView, emptyLetterView);
            }
            dragging = false;
            eventConsumed = false;

        } else if (action == MotionEvent.ACTION_MOVE) {
            if (v != letterView) {
                if (dragging) {
                    setAbsoluteLocationCentered(letterView, x, y);
                }
            }
        }

        return eventConsumed;

    }


    private void setSameAbsoluteLocation(View v1, View v2) {
        AbsoluteLayout.LayoutParams alp2 = (AbsoluteLayout.LayoutParams) v2.getLayoutParams();
        setAbsoluteLocation(v1, alp2.x, alp2.y);
    }


    private void setAbsoluteLocationCentered(View v, int x, int y) {
        setAbsoluteLocation(v, x - v.getWidth() / 2, y - v.getHeight() / 2);
    }


    private void setAbsoluteLocation(View v, int x, int y) {
        AbsoluteLayout.LayoutParams alp = (AbsoluteLayout.LayoutParams) v.getLayoutParams();
        alp.x = x;
        alp.y = y;
        v.setLayoutParams(alp);
    }
}

这就是我一直在实现的我只是添加新变量并将其更改为 letterView1 和 emptyLetterView1

Java 文件:

package edu.sbcc.cs123.draganddropbasic;

import android.app.*;
import android.graphics.*;
import android.os.*;
import android.view.*;
import android.view.View.*;
import android.widget.*;

@SuppressWarnings("deprecation")
public class DragAndDropBasicActivity extends Activity implements OnTouchListener {
    private ImageView letterView;                       // The letter that the user drags.
    private ImageView emptyLetterView;          // The letter outline that the user is supposed to drag letterView to.
    private ImageView letterView1;                      // The letter that the user drags.
    private ImageView emptyLetterView1; 
    private AbsoluteLayout mainLayout;


    /** Called when the activity is first created. */
    @Override
    public void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);

        mainLayout = (AbsoluteLayout) findViewById(R.id.mainLayout);
        mainLayout.setOnTouchListener(this);
        letterView = (ImageView) findViewById(R.id.letterView);
        letterView.setOnTouchListener(this);

        emptyLetterView = (ImageView) findViewById(R.id.emptyLetterView);

        letterView1 = (ImageView) findViewById(R.id.letterView1);
        letterView1.setOnTouchListener(this);

        emptyLetterView1 = (ImageView) findViewById(R.id.emptyLetterView1);
    }

    private boolean dragging = false;
    private Rect hitRect = new Rect();

    @Override
    /**
     * NOTE:  Had significant problems when I tried to react to ACTION_MOVE on letterView.   Kept getting alternating (X,Y) 
     * locations of the motion events, which caused the letter to flicker and move back and forth.  The only solution I could 
     * find was to determine when the user had touched down on the letter, then process moves in the ACTION_MOVE 
     * associated with the mainLayout.
     */
    public boolean onTouch(View v, MotionEvent event) {
        boolean eventConsumed = true;
        int x = (int)event.getX();
        int y = (int)event.getY();

        int action = event.getAction();
        if (action == MotionEvent.ACTION_DOWN) {
            if (v == letterView) {
                dragging = true;
                eventConsumed = false;
            }
            if (v == letterView1) {
                dragging = true;
                eventConsumed = false;
            }
        } else if (action == MotionEvent.ACTION_UP) {

            if (dragging) {
                emptyLetterView.getHitRect(hitRect);
                if (hitRect.contains(x, y))
                    setSameAbsoluteLocation(letterView, emptyLetterView);
            }

            if (dragging) {
                emptyLetterView1.getHitRect(hitRect);
                if (hitRect.contains(x, y))
                    setSameAbsoluteLocation1(letterView1, emptyLetterView1);
            }
            dragging = false;
            eventConsumed = true;

        } else if (action == MotionEvent.ACTION_MOVE) {
            if (v != letterView) {
                if (dragging) {
                    setAbsoluteLocationCentered(letterView, x, y);
                }
            }
            if (v != letterView1) {
                if (dragging) {
                    setAbsoluteLocationCentered1(letterView1, x, y);
                }
            }
        }

        return eventConsumed;

    }


    private void setSameAbsoluteLocation(View v1, View v2) {
        AbsoluteLayout.LayoutParams alp2 = (AbsoluteLayout.LayoutParams) v2.getLayoutParams();
        setAbsoluteLocation(v1, alp2.x, alp2.y);
    }


    private void setAbsoluteLocationCentered(View v, int x, int y) {
        setAbsoluteLocation(v, x - v.getWidth() / 2, y - v.getHeight() / 2);
    }


    private void setAbsoluteLocation(View v, int x, int y) {
        AbsoluteLayout.LayoutParams alp = (AbsoluteLayout.LayoutParams) v.getLayoutParams();
        alp.x = x;
        alp.y = y;
        v.setLayoutParams(alp);
    }




    private void setSameAbsoluteLocation1(View v1, View v2) {
        AbsoluteLayout.LayoutParams alp2 = (AbsoluteLayout.LayoutParams) v2.getLayoutParams();
        setAbsoluteLocation1(v1, alp2.x, alp2.y);
    }


    private void setAbsoluteLocationCentered1(View v, int x, int y) {
        setAbsoluteLocation1(v, x - v.getWidth() / 2, y - v.getHeight() / 2);
    }


    private void setAbsoluteLocation1(View v, int x, int y) {
        AbsoluteLayout.LayoutParams alp = (AbsoluteLayout.LayoutParams) v.getLayoutParams();
        alp.x = x;
        alp.y = y;
        v.setLayoutParams(alp);
    }
}

我已将图像文件添加到 xml 文件并将 id 更改为 letterView1 和 emptyLetterView1。

所以另一张图片显示成功，然而，当我拖动其中一张图片时，另一张图片消失了。

请问我该如何实现？

Answer 1

我会将您的解决方案基于以下代码/信息:

• 拖放 official guide
• 来自 SDK 的样本:DragAndDrop & DragableDot
• Vogella 关于 Drag and Drop 的教程
• 关于拖放的三部分博文 1 , 2和 3