安卓-07-开发自定义的View

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

 1 <?xml version="1.0" encoding="utf-8"?>
 2 <FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
 3     xmlns:app="http://schemas.android.com/apk/res-auto"
 4     xmlns:tools="http://schemas.android.com/tools"
 5     android:id="@+id/mylayout"
 6     android:layout_width="match_parent"
 7     android:layout_height="match_parent"
 8     android:background="@mipmap/earth"
 9     tools:context=".MainActivity">
10 
11 </FrameLayout>

---

创建Rabbit类

 1 package com.example.myview;
 2 
 3 import android.content.Context;
 4 import android.graphics.Bitmap;
 5 import android.graphics.BitmapFactory;
 6 import android.graphics.Canvas;
 7 import android.graphics.Paint;
 8 import android.view.View;
 9 
10 public class RabbitView extends View {
11     public float bitmapX;
12     public float bitmapY;
13     public RabbitView(Context context) {
14         super(context);
15         bitmapX = 290;
16         bitmapY = 130;
17     }
18 
19     @Override
20     protected void onDraw(Canvas canvas) {
21         super.onDraw(canvas);
22         Paint paint = new Paint();  // 创建画笔对象
23         Bitmap bitmap = BitmapFactory.decodeResource(this.getResources(), R.mipmap.robbit);  // 设置图像, 将兔子图片作为参数传入
24         canvas.drawBitmap(bitmap, bitmapX, bitmapY, paint);  // 通过canvas组件画出兔子
25         if(bitmap.isRecycled()) {  // 回收
26             bitmap.recycle();
27         }
28     }
29 }

---

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

 1 package com.example.myview;
 2 
 3 import android.support.v7.app.AppCompatActivity;
 4 import android.os.Bundle;
 5 import android.view.MotionEvent;
 6 import android.view.View;
 7 import android.widget.FrameLayout;
 8 
 9 public class MainActivity extends AppCompatActivity {
10 
11     @Override
12     protected void onCreate(Bundle savedInstanceState) {
13         super.onCreate(savedInstanceState);
14         setContentView(R.layout.activity_main);
15         FrameLayout frameLayout = findViewById(R.id.mylayout);
16         final RabbitView rabbitView = new RabbitView(this);
17         rabbitView.setOnTouchListener(new View.OnTouchListener() {
18             @Override
19             public boolean onTouch(View v, MotionEvent event) {
20                 rabbitView.bitmapX = event.getX();
21                 rabbitView.bitmapY = event.getY();
22                 rabbitView.invalidate();
23                 return true;
24             }
25         });
26         frameLayout.addView(rabbitView);
27     }
28 }