Android动态壁纸详解

动态壁纸

Livewallpaper（动态壁纸）： 首先动态壁纸并不是GIF图片，而是一个独立的应用程序,本质是一个Service,甚至可以没有桌面图标。

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直接看AndroidManifest.xml

"1.0" encoding="utf-8"?>
"http://schemas.android.com/apk/res/android"
    package="com.qwq.clocklivewallpaper">

    "true"
        android:icon="@drawable/clock"
        android:label="@string/app_name"
        android:supportsRtl="true"
        android:theme="@style/AppTheme">

        
        ".MainActivity">
            
                "android.intent.action.MAIN" />
                "android.intent.category.LAUNCHER" />
            
        

        
        ".SettingsActivity"
            android:exported="true"
            android:label="@string/app_name">
        

        
        ".ClockWallpaperService"
            android:enabled="true"
            android:label="@string/wallpaper_name" //下面第一张图片中label
            android:permission="android.permission.BIND_WALLPAPER">//动态壁纸必须加此权限

            
                //系统就是通过APK的这个action把其当做一个动态墙纸。
              "android.service.wallpaper.WallpaperService">
            

            
            "android.service.wallpaper"
                android:resource="@xml/clock_wallpaper">
            

        
    

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clock_wallpaper.xml

"1.0" encoding="UTF-8"?>
"http://schemas.android.com/apk/res/android"
    android:description="@string/wallpaper_description"
    android:settingsActivity="com.qwq.clocklivewallpaper.SettingsActivity"
    android:thumbnail="@drawable/ic_preview" />

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android:thumbnail 动态壁纸列表中的图标，
android:description 动态壁纸的简单介绍文字，有的手机可能不显示

android:settingsActivity 指定一个Activity。系统会检测动态壁纸应用有没有此属性。如果有则和下方的图片显示效果一样（两个Button），点击下图中设定Button可跳转至指定的Activity（设置界面）。如果没有此属性，就只有一个设置壁纸Button。可以去掉此属性看一下效果。

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WallpaperService（核心）

实现动态壁纸必须继承WallpaperService，且重载onCreateEngine方法。onCreateEngine()方法只需返回一个Engine的子类对象就可以了，所以动态壁纸应用的主要工作就是实现Engine的子类。其原理是使用surfaceview不断更新,实现动态壁纸效果。不多说了，直接贴代码，重要的方法都会有所说明。

package com.qwq.clocklivewallpaper;

import android.content.SharedPreferences;
import android.content.SharedPreferences.OnSharedPreferenceChangeListener;
import android.graphics.Canvas;
import android.graphics.Color;
import android.graphics.Paint;
import android.os.Handler;
import android.preference.PreferenceManager;
import android.service.wallpaper.WallpaperService;
import android.util.Log;
import android.view.MotionEvent;
import android.view.SurfaceHolder;

import java.util.Date;

public class ClockWallpaperService extends WallpaperService {

    static final String TAG = ClockWallpaperService.class.getSimpleName();
    static final int POINTER_WIDTH = 9;

  //  onCreateEngine()方法需返回一个Engine的子类对象就可以了，
  //  所以动态壁纸应用的主要工作就是实现Engine的子类
  @Override
  public Engine onCreateEngine() {
        Log.d(TAG, "onCreateEngine");
        return new ClockWallpaperEngine();
    }


    //实现Engine的子类，本文的重中之重，动态壁纸就是在此具体实现的
  private class ClockWallpaperEngine extends Engine implements 
  OnSharedPreferenceChangeListener {
        private final Handler handler = new Handler();
        // surfacewive使用线程更新UI，所以我们可使用Runnable接口创建一个线程，把具体绘制方法放进去，
        // 下文会使用handler调用
        private final Runnable drawRunner = new Runnable() {
            @Override
            public void run() {
                draw();
            }
        };

        private Paint paint;
        private int width;
        private int height;
        private boolean isVisible = true;
        private boolean isShowSecond;
        private ClockView clockView;
        private SharedPreferences sp;

 //构造函数，初始化动态壁纸
 public ClockWallpaperEngine() {
            Log.d(TAG, "ClockWallpaperEngine");
            initSp();
            initPaint();
            startDrawClock();
        }

  public void initSp() {
         sp = PreferenceManager.getDefaultSharedPreferences(ClockWallpaperService.this);
         sp.registerOnSharedPreferenceChangeListener(this);
         isShowSecond = sp.getBoolean(SettingsActivity.IS_SHOW_SECOND, true);
        }

  public void initPaint() {
            paint = new Paint();
            paint.setAntiAlias(true);
            paint.setStyle(Paint.Style.STROKE);
            paint.setStrokeWidth(POINTER_WIDTH);
        }

   public void startDrawClock() {
            clockView = new ClockView(getApplicationContext());
            handler.post(drawRunner);
        }

   @Override
   public void onCreate(SurfaceHolder surfaceHolder) {
            super.onCreate(surfaceHolder);
            Log.d(TAG, "onCreate");
        }


   //监听是否可见变化，可见时开始更新UI,不可见时停止刷新
   @Override
   public void onVisibilityChanged(boolean visible) {
            this.isVisible = visible;
            if (visible) {
                handler.post(drawRunner);
            } else {
                handler.removeCallbacks(drawRunner);
            }
        }

   @Override
   public void onSurfaceDestroyed(SurfaceHolder holder) {
            super.onSurfaceDestroyed(holder);
            isVisible = false;
            handler.removeCallbacks(drawRunner);
            sp.unregisterOnSharedPreferenceChangeListener(this);
        }


   @Override
   public void onSurfaceChanged(SurfaceHolder holder,int format,int width,int height){    
            this.width = width;
            this.height = height;
            super.onSurfaceChanged(holder, format, width, height);
        }

   //绘制，每个200毫秒刷新界面
   private void draw() {
            SurfaceHolder holder = getSurfaceHolder();
            Canvas canvas = null;
            try {
                canvas = holder.lockCanvas();
                if (canvas != null) {
                    drawClock(canvas);
                }
            } finally {
                if (canvas != null) {
                    holder.unlockCanvasAndPost(canvas);
                }
            }

            handler.removeCallbacks(drawRunner);
            if (isVisible) {
                handler.postDelayed(drawRunner, 200);
            }
        }

  //具体绘制钟表
  private void drawClock(Canvas canvas) {
       canvas.drawColor(Color.WHITE);   //绘制整个动态壁纸的背景颜色
       clockView.config(width / 2, height / 2, (int) (width * 0.8f), new Date(), 
       paint, isShowSecond);
       clockView.draw(canvas);
        }

  @Override
  public void onSharedPreferenceChanged(SharedPreferences sharedPreferences, String 
  key){ 
     //监听SharedPreference变化，改变动态壁纸样式
     if (SettingsActivity.IS_SHOW_SECOND.equals(key)) {
     isShowSecond = sharedPreferences.getBoolean(SettingsActivity.IS_SHOW_SECOND,  
     true);
            }
        }

   @Override
   public void onTouchEvent(MotionEvent event) {
            super.onTouchEvent(event);
            // 可以在这里做一些与用户交互的操作，例如动态星星壁纸，用户触摸屏幕时增加星星数量。
            Log.d(TAG, "onTouchEvent");
        }
    }

}

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ClockView（钟表的具体绘制）

package com.qwq.clocklivewallpaper;

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

import java.util.Calendar;
import java.util.Date;

public class ClockView extends View {

    static final String TAG = ClockView.class.getSimpleName();
    private float x;
    private float y;
    private int radius;
    private Calendar cal;
    private Paint paint;
    private Bitmap clockDial = BitmapFactory.decodeResource(getResources(),R.drawable.clock_bg);
    private int sizeScaled = -1;
    private Bitmap clockDialScaled;
    private boolean isShowSecond;

    public ClockView(Context context) {
        super(context);
        cal = Calendar.getInstance();
    }

//设置钟表宽高等属性
public void config(float x, float y, int size, Date date, Paint paint, boolean 
    isShowSecond) {
        this.x = x;
        this.y = y;
        this.paint = paint;
        this.isShowSecond = isShowSecond;

        cal.setTime(date);

        if (size != sizeScaled) {
            clockDialScaled = Bitmap.createScaledBitmap(clockDial, size, size, false);
            radius = size / 2;
        }
    }

//具体绘制钟表的指针
protected void onDraw(Canvas canvas) {
   Log.d(TAG,"onDraw:"+canvas);
   super.onDraw(canvas);
   if (paint != null) {
            canvas.drawBitmap(clockDialScaled, x - radius, y - radius, null);

            float sec = cal.get(Calendar.SECOND);
            float min = cal.get(Calendar.MINUTE);
            float hour = cal.get(Calendar.HOUR_OF_DAY);


   paint.setColor(Color.RED);
   canvas.drawLine(x, y,
   (float)(x + (radius * 0.5f)*Math.cos(Math.toRadians((hour / 12.0f * 360.0f) - 90f))),
   (float)(y + (radius * 0.5f)*Math.sin(Math.toRadians((hour / 12.0f * 360.0f) -90f))),   
   paint);
   canvas.save();

    paint.setColor(Color.BLUE);
    canvas.drawLine(x, y, 
    (float)(x + (radius * 0.6f)*Math.cos(Math.toRadians((min / 60.0f * 360.0f) - 90f))),
    (float)(y + (radius * 0.6f)*Math.sin(Math.toRadians((min / 60.0f * 360.0f) - 90f))),  
    paint);
    canvas.save();

    if (isShowSecond) {
       paint.setColor(Color.GREEN);
       canvas.drawLine(x, y,
       (float)(x + (radius * 0.7f)*Math.cos(Math.toRadians((sec/60.0f * 360.0f) - 90f))),
       (float)(y + (radius * 0.7f)*Math.sin(Math.toRadians((sec/60.0f * 360.0f) - 90f))),   
       paint);
          }
        }
    }

}

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