自定义View的编写

Posted 2020-06-17

在项目的时候，很多情况要用到自定义View来达到自己想要的效果，所有自定义View的编写很重要。

 

首先看看所要实现的效果：

 

最上面的一行字“LogicView”每次从左向右滚动，下面的圆从角度0到360不断变化。并且颜色随机地变化。

 

MainActivity.java

 1 package com.example.myview;
 2 
 3 import android.os.Bundle;
 4 import android.app.Activity;
 5 import android.view.Menu;
 6 
 7 public class MainActivity extends Activity {
 8 
 9     @Override
10     protected void onCreate(Bundle savedInstanceState) {
11         super.onCreate(savedInstanceState);
12         setContentView(R.layout.activity_main);
13         //setContentView(new Myview(this));
14     }
15 }

 

activity_main.xml

 1 <FrameLayout xmlns:android="http://schemas.android.com/apk/res/android"
 2     xmlns:tools="http://schemas.android.com/tools"
 3     android:layout_width="match_parent"
 4     android:layout_height="match_parent"
 5     tools:context=".MainActivity" >
 6     <com.example.myview.TestClass      
 7         android:layout_width="match_parent"
 8         android:layout_height="match_parent"
 9    
10         />
11 </FrameLayout>

 

TestClass.java

 1 package com.example.myview;
 2 
 3 import java.util.Random;
 4 
 5 import android.content.Context;
 6 import android.graphics.Canvas;
 7 import android.graphics.Paint;
 8 import android.graphics.RectF;
 9 import android.util.AttributeSet;
10 import android.view.View;
11 
12 public  class TestClass extends View{
13 
14     private MyThread thread;
15     private Paint paint = new Paint();
16     private float rx = 0;
17     private RectF rectF = new RectF(0,60,100,160);
18     private float sweepAngel = 0;
19     Random rand = new Random();
20     
21     public TestClass(Context context, AttributeSet attrs) {
22         super(context, attrs);
23     }
24 
25     public TestClass(Context context) {
26         super(context);
27     }
28     
29     private  void drawSub(Canvas canvas){
30         paint.setTextSize(30);
31         canvas.drawText("LogicView", rx, 30, paint);
32         
33         canvas.drawArc(rectF,0,sweepAngel,true,paint);
34     }
35     
36     protected void onDraw(Canvas canvas){
37         if(thread==null){
38             thread = new MyThread();
39             thread.start();
40         }else{
41             drawSub(canvas);
42         }
43     }
44     
45     private void logic(){
46         rx++;
47         if(rx > getWidth()){
48             rx = 0 - paint.measureText("LogicView");
49         }
50         
51         sweepAngel ++ ;
52         
53         if(sweepAngel > 360){
54             sweepAngel = 0; 
55         }
56         int r = rand.nextInt(256);
57         int g = rand.nextInt(256);
58         int b = rand.nextInt(256);
59         paint.setARGB(255, r, g, b);
60     }
61     
62     class MyThread extends Thread{
63         @Override
64         public void run() {
65             while(true){
66                 logic();
67                 postInvalidate();
68                 try {
69                     Thread.sleep(30);
70                 } catch (InterruptedException e) {
71                     e.printStackTrace();
72                 }
73             }
74             
75         }
76     }
77     
78 }