Android: Drag and Drop UI

Recently, I was busy with some UI special effects. I thought this was not something we developed, but it was something designers should manage. A recent headache, there is no way to do it. I still have to do it slowly. I have a sense of responsibility for development. I have found this item in China and I am not very clear about it. Most of it is about using windowmanager to manage the UI components to be dragged. But after I have done so, I feel troublesome, it is not what I want. Didn't the parent container be used to control the UI drag implementation? The answer is yes. I found the following materials and found that the results are good and helpful. Let's share it with you:

<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/vg"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent"
    android:orientation="vertical" >

<ImageView
android:id="@+id/img"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:src="@drawable/ic_launcher" />

</LinearLayout>

The code is very simple. The main idea is to set a view for the UI you want to drag. ontouchlistener, and then set your own view in the viewgroup you want to implement. ontouchlistener. when the UI is moved, you can obtain the displacement data and reset the layout attribute of the UI in the viewgroup containing the UI. The Code is as follows:

package com.android.drag_drop;

import android.app.Activity;
import android.os.Bundle;
import android.view.MotionEvent;
import android.view.View;
import android.view.ViewGroup;
import android.widget.ImageView;
import android.widget.LinearLayout;

public class MainActivity extends Activity {
private View selected_item = null;
private int offset_x = 0;
private int offset_y = 0;

    @Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        ViewGroup vg = (ViewGroup) findViewById(R.id.vg);
        vg.setOnTouchListener(new View.OnTouchListener() {

            @Override
public boolean onTouch(View v, MotionEvent event) {
switch (event.getActionMasked()) {
case MotionEvent.ACTION_MOVE:
int x = (int) event.getX() - offset_x;
int y = (int) event.getY() - offset_y;

int w = getWindowManager().getDefaultDisplay().getWidth() - 100;
int h = getWindowManager().getDefaultDisplay().getHeight() - 100;
if (x > w)
                        x = w;
if (y > h)
                        y = h;
                    LinearLayout.LayoutParams lp = new LinearLayout.LayoutParams(
new ViewGroup.MarginLayoutParams(
                                    LinearLayout.LayoutParams.WRAP_CONTENT,
                                    LinearLayout.LayoutParams.WRAP_CONTENT));
                    lp.setMargins(x, y, 0, 0);

                    selected_item.setLayoutParams(lp);
break;
default:
break;
                }
return true;
            }
        });
        ImageView img = (ImageView) findViewById(R.id.img);
        img.setOnTouchListener(new View.OnTouchListener() {

            @Override
public boolean onTouch(View v, MotionEvent event) {
switch (event.getActionMasked()) {
case MotionEvent.ACTION_DOWN:
                    offset_x = (int) event.getX();
                    offset_y = (int) event.getY();
                    selected_item = v;
break;
default:
break;
                }

return false;
            }
        });
    }
}

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