Android学习笔记触摸事件

案例代码:

activity_main.xml

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:id="@+id/relativeLayout"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="@drawable/bg"
    tools:context=".MainActivity">

</RelativeLayout>

AndroidView.java

package com.example.demo4;

import android.content.Context;
import android.graphics.Bitmap;
import android.graphics.BitmapFactory;
import android.graphics.Canvas;
import android.graphics.Paint;
import android.view.View;

/**
 * 创建自定义View，用来绘制安卓的logo
 */
public class AndroidView extends View {

    public float bitmapX;
    public float bitmapY;

    public AndroidView(Context context) {
        super(context);
        bitmapX = 65;
        bitmapY = 0;
    }

    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);
        Paint paint = new Paint();
        Bitmap bitmap = BitmapFactory.decodeResource(
                this.getResources(),R.mipmap.ic_launcher);
        canvas.drawBitmap(bitmap,bitmapX,bitmapY,paint);
        if(bitmap.isRecycled()){
            bitmap.recycle();
        }
    }
}

MainActivity.java

package com.example.demo4;

import androidx.appcompat.app.AppCompatActivity;
import android.os.Bundle;
import android.view.MotionEvent;
import android.view.View;
import android.widget.RelativeLayout;

public class MainActivity extends AppCompatActivity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        /**
         *第二步:创建并示例化帽子类的一个对象，并为AndroidLogo添加触摸
         * 事件监听器，在重写的触摸方法中根据触摸的位置重新绘制
         * Logo
         */
        final AndroidView androidView = new AndroidView(MainActivity.this);

        androidView.setOnTouchListener(new View.OnTouchListener(){
            @Override
            public boolean onTouch(View v, MotionEvent event) {
                androidView.bitmapX = event.getX() - 80;
                androidView.bitmapY = event.getY() - 80;
                androidView.invalidate();
                return true;
            }
        });
        //第三步:把Logo添加到布局管理器中
        RelativeLayout rl = (RelativeLayout)findViewById
                (R.id.relativeLayout);
        rl.addView(androidView);
    }
}