安卓-07-开发自定义的View--实践-跟随手指移动的小兔子

通常不实用View和ViewGroup类

可以使用继承View的自定义的View类

思路是:

创建继承View的自定义类, 在MainActivity.java 中创建自定义类的对象

实践--跟随手指移动的小兔子

---

XML : 设置背景图片, id

<?xml version="1.0" encoding="utf-8"?>
<FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:id="@+id/mylayout"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:background="@mipmap/earth"
    tools:context=".MainActivity">

</FrameLayout>

---

创建Rabbit类

package com.example.myview;

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

public class RabbitView extends View {
    public float bitmapX;
    public float bitmapY;
    public RabbitView(Context context) {
        super(context);
        bitmapX = 290;
        bitmapY = 130;
    }

    @Override
    protected void onDraw(Canvas canvas) {
        super.onDraw(canvas);
        Paint paint = new Paint();  // 创建画笔对象
        Bitmap bitmap = BitmapFactory.decodeResource(this.getResources(), R.mipmap.robbit);  // 设置图像, 将兔子图片作为参数传入
        canvas.drawBitmap(bitmap, bitmapX, bitmapY, paint);  // 通过canvas组件画出兔子
        if(bitmap.isRecycled()) {  // 回收
            bitmap.recycle();
        }
    }
}

---

在MainActivity.java类中创建Rabbit类的对象并设置Touch事件

package com.example.myview;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.MotionEvent;
import android.view.View;
import android.widget.FrameLayout;

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        FrameLayout frameLayout = findViewById(R.id.mylayout);
        final RabbitView rabbitView = new RabbitView(this);
        rabbitView.setOnTouchListener(new View.OnTouchListener() {
            @Override
            public boolean onTouch(View v, MotionEvent event) {
                rabbitView.bitmapX = event.getX();
                rabbitView.bitmapY = event.getY();
                rabbitView.invalidate();
                return true;
            }
        });
        frameLayout.addView(rabbitView);
    }
}