android 之 StrictMode

桃扇骨 2022-09-24 14:23 153阅读 0赞

StrictMode类是[Android][] 2.3 （API 9）引入的一个工具类，可以用来帮助开发者发现代码中的一些不规范的问题。比如，如果你在UI线程中进行了网络或者磁盘操作，StrictMode就会通过Log（logcat ）或者对话框的方式把信息提示给你，因为让你的UI线程处理这里操作会被认为是不规范的做法，可能会让你的应用变得比较卡顿。

官网文档：[http://developer.android.com/reference/android/os/StrictMode.html][http_developer.android.com_reference_android_os_StrictMode.html]

# 如何启用 StrictMode #

我们通常在 Activity 或者自定义的Application类中启动 StrictMode，代码如下：

public void onCreate() { 
         if (DEVELOPER_MODE) { 
             StrictMode.setThreadPolicy(new StrictMode.ThreadPolicy.Builder()
                     .detectDiskReads()
                     .detectDiskWrites()
                     .detectNetwork()   // or .detectAll() for all detectable problems
                     .penaltyLog()
                     .build());
             StrictMode.setVmPolicy(new StrictMode.VmPolicy.Builder()
                     .detectLeakedSqlLiteObjects()
                     .detectLeakedClosableObjects()
                     .penaltyLog()
                     .penaltyDeath()
                     .build());
         }
         super.onCreate();
     }

注意：我们只需要在app的开发版本下使用 StrictMode，线上版本避免使用 StrictMode，随意需要通过 诸如 DEVELOPER\_MODE 这样的配置变量来进行控制。

下面我们举几个例子来说明 StrictMode 是如何发挥作用的。

代码1：

public class ActivitySimple extends Activity { 
    
        @Override
        protected void onCreate(Bundle savedInstanceState) { 
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_main);
    
            StrictMode.setThreadPolicy(new ThreadPolicy.Builder()
                    .detectAll()
                    .penaltyDialog() //弹出违规提示对话框
                    .penaltyLog() //在Logcat 中打印违规异常信息
                    .build());
            
            this.testNetwork();
        }
    
        
        private void testNetwork() { 
            try { 
                URL url = new URL("http://www.baidu.com");
                HttpURLConnection conn = (HttpURLConnection) url.openConnection();
                conn.connect();
                BufferedReader reader = new BufferedReader(new InputStreamReader(
                        conn.getInputStream()));
                String lines = null;
                StringBuffer sb = new StringBuffer();
                while ((lines = reader.readLine()) != null) { 
                    sb.append(lines);
                }
            } catch (Exception e) { 
                e.printStackTrace();
            }
        }
    }

在这里例子中，我们在主线程（UI线程）中执行了网络请求，ThreadPolicy 策略中的 `detectAll()`方法 包含而来对这类违规操作的检查，同时我们通过`penaltyDialog()` 和 `penaltyLog()` 两个方法将违规信息提示给开发者。

在运行这段代码是，我们会看到下图中的对话框提示：

![dialog.png][]

在LogCat 中我们会看到这样的日志信息：

... D/StrictMode(26365): StrictMode policy violation; ~duration=58 ms: android.os.StrictMode$StrictModeNetworkViolation: policy=63 violation=4
    ... D/StrictMode(26365):    at android.os.StrictMode$AndroidBlockGuardPolicy.onNetwork(StrictMode.java:1134)
    ... D/StrictMode(26365):    at libcore.io.BlockGuardOs.recvfrom(BlockGuardOs.java:163)
    ... D/StrictMode(26365):    at libcore.io.IoBridge.recvfrom(IoBridge.java:557)
    ... D/StrictMode(26365):    at java.net.PlainSocketImpl.read(PlainSocketImpl.java:490)
    ... D/StrictMode(26365):    at java.net.PlainSocketImpl.access$000(PlainSocketImpl.java:46)
    ...
    （后面的部分省略）

# StrictMode 详解 #

StrictMode 通过策略方式来让你自定义需要检查哪方面的问题。 主要有两中策略，一个时线程方策略（[ThreadPolicy][]），一个是VM方面的策略（[VmPolicy][]）。

*  ThreadPolicy 主要用于发现在UI线程中是否有读写磁盘的操作，是否有网络操作，以及检查UI线程中调用的自定义代码是否执行得比较慢。
 *  VmPolicy，主要用于发现内存问题，比如 Activity内存泄露， SQL 对象内存泄露， 资源未释放，能够限定某个类的最大对象数。

## ThreadPolicy 详解 ##

[StrictMode.ThreadPolicy.Builder][] 主要方法如下：

*  detectNetwork() 用于检查UI线程中是否有网络请求操作，上面的代码的就是网络请求违规的问题。
 *  detectDiskReads() 和 detectDiskReads() 是磁盘读写检查，触发时会打印出如下日志（以 detectDiskReads() 为例）：
    
        ... D/StrictMode(27429): StrictMode policy violation; ~duration=33 ms: android.os.StrictMode$StrictModeDiskReadViolation: policy=31 violation=2
        ... D/StrictMode(27429):    at android.os.StrictMode$AndroidBlockGuardPolicy.onReadFromDisk(StrictMode.java:1118)
        ... D/StrictMode(27429):    at libcore.io.BlockGuardOs.open(BlockGuardOs.java:106)
        ... D/StrictMode(27429):    at java.io.File.createNewFile(File.java:941)
        ... D/StrictMode(27429):    at com.ap.teststrictmode.ActivityTestDisk.testWriteDisk(ActivityTestDisk.java:51)
        ... D/StrictMode(27429):    at com.ap.teststrictmode.ActivityTestDisk.onCreate(ActivityTestDisk.java:40)
        ... D/StrictMode(27429):    at android.app.Activity.performCreate(Activity.java:5122)
        ... D/StrictMode(27429):    at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1081)
        ... D/StrictMode(27429):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2270)
        ...
        （后面的部分省略）
 *  detectCustomSlowCalls() 主要用于帮助开发者发现UI线程调用的那些方法执行得比较慢，要和 `StrictMode.noteSlowCall` 配合使用，`StrictMode.noteSlowCall` 只有通过 `StrictMode.noteSlowCall`用来标记“可能会”执行比较慢的方法，只有标记过的方法才能被检测到，日志中会记录方法的执行时间（比如 ~duration=2019 ms）。看下面的例子：   
    代码2：
    
        public class ActivityTestDetectCustomSlowCalls extends Activity { 
        
         private TextView textView = null;
        
         private static boolean isStrictMode = false;
        
         @Override
        protected void onCreate(Bundle savedInstanceState) { 
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activitymain);
            this.textView = (TextView) findViewById(R.id.textview);
            this.textView.setText("In ActivityTestDetectCustomSlowCalls");
            if(! isStrictMode){ 
                StrictMode.setThreadPolicy(new ThreadPolicy.Builder()
                        .detectCustomSlowCalls()
                        .penaltyLog()
                        .build());
                isStrictMode = true;
            }
            this.slowCall1();
            this.slowCall2();
        }
        
         /*
         * 没有标记的方法
         */
        private void slowCall_1(){ 
            //用来标记潜在执行比较慢的方法
            SystemClock.sleep(1000  2);
        }
        
         / * 标记过的方法 / private void slowCall_2(){ //用来标记潜在执行比较慢的方法 StrictMode.noteSlowCall("slowCall 2"); SystemClock.sleep(1000 2); } }
    
      
    在logcat 中我们只能看到和方法 `slowCall_2()`（因为通过`StrictMode.noteSlowCall()`标记过）相关的日志：  
    
    
        ...: D/StrictMode(1349): StrictMode policy violation; **~duration=2019 ms: android.os.StrictMode$StrictModeCustomViolation: policy=24 violation=8 msg=slowCall 2
        ...: D/StrictMode(1349):    at android.os.StrictMode$AndroidBlockGuardPolicy.onCustomSlowCall(StrictMode.java:1105)
        ...: D/StrictMode(1349):    at android.os.StrictMode.noteSlowCall(StrictMode.java:1903)
        ...: D/StrictMode(1349):    at com.ap.teststrictmode.ActivityTestDetectCustomSlowCalls.slowCall_2(ActivityTestDetectCustomSlowCalls.java:52)
        ...: D/StrictMode(1349):    at com.ap.teststrictmode.ActivityTestDetectCustomSlowCalls.onCreate(ActivityTestDetectCustomSlowCalls.java:35)
        ...: D/StrictMode(1349):    at android.app.Activity.performCreate(Activity.java:5122)
        ...: D/StrictMode(1349):    at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1081)
        ...: D/StrictMode(1349):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2270)
        ...: D/StrictMode(1349):    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2358)
        ...: D/StrictMode(1349):    at android.app.ActivityThread.access$600(ActivityThread.java:156)
        ...: D/StrictMode(1349):    at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1340)
        ...: D/StrictMode(1349):    at android.os.Handler.dispatchMessage(Handler.java:99)
        ...: D/StrictMode(1349):    at android.os.Looper.loop(Looper.java:153)
        ...
        （后面的部分省略）
    
      
    当然你也可以在其他线程中使用 detectCustomSlowCalls()，但是没有什么实际意义，也看不到方法执行时间，比如：

public class ActivityTestDetectCustomSlowCalls extends Activity { 
        
        private TextView textView = null;
        
        @Override
        protected void onCreate(Bundle savedInstanceState) { 
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_main);
    
            this.textView = (TextView) findViewById(R.id.text_view);
            
            this.textView.setText("In ActivityTestDetectCustomSlowCalls");
            
            new Thread(){ 
                public void run() { 
                    StrictMode.setThreadPolicy(new ThreadPolicy.Builder()
                        .detectCustomSlowCalls()
                        .penaltyLog()
                        .build());
                    
                    this.slowCallInCustomThread();
                };
                
                private void slowCallInCustomThread(){ 
                    //用来标记潜在执行比较慢的方法
                    StrictMode.noteSlowCall("slowCallInCustomThread");
                    SystemClock.sleep(1000 * 2);
                }            
            }.start();;
        }
    }

日志输出如下：

...: D/StrictMode(2418): StrictMode policy violation: android.os.StrictMode$StrictModeCustomViolation: policy=24 violation=8 msg=slowCallInCustomThread
    ...: D/StrictMode(2418):    at android.os.StrictMode$AndroidBlockGuardPolicy.onCustomSlowCall(StrictMode.java:1105)
    ...: D/StrictMode(2418):    at android.os.StrictMode.noteSlowCall(StrictMode.java:1903)
    ...: D/StrictMode(2418):    at com.ap.teststrictmode.ActivityTestDetectCustomSlowCalls$1.slowCallInCustomThread(ActivityTestDetectCustomSlowCalls.java:35)
    ...: D/StrictMode(2418):    at com.ap.teststrictmode.ActivityTestDetectCustomSlowCalls$1.run(ActivityTestDetectCustomSlowCalls.java:30)
    ...
    （后面的部分省略）

*  penaltyDeath()，当触发违规条件时，直接Crash掉当前应用程序。
 *  penaltyDeathOnNetwork()，当触发网络违规时，Crash掉当前应用程序。
 *  penaltyDialog()，触发违规时，显示对违规信息对话框。
 *  penaltyFlashScreen()，会造成屏幕闪烁，不过一般的设备可能没有这个功能。
 *  penaltyDropBox()，将违规信息记录到 dropbox 系统日志目录中（/data/system/dropbox），你可以通过如下命令进行插件：
    
        adb shell dumpsys dropbox dataappstrictmode  --print
    
    会得到如下的信息：
    
        2014-05-04 14:56:32 dataappstrictmode (text, 2627 bytes)
        Process: com.ap.teststrictmode
        Flags: 0x40a8be46
        Package: com.ap.teststrictmode v1 (1.0)
        Build: Xiaomi/pisces/pisces:4.2.1/JOP40D/JXCCNBA13.0:user/release-keys
        System-App: false
        Uptime-Millis: 66679049
        Loop-Violation-Number: 10
        Duration-Millis: 24
        android.os.StrictMode$StrictModeNetworkViolation: policy=191 violation=4
            at android.os.StrictMode$AndroidBlockGuardPolicy.onNetwork(StrictMode.java:1136)
            at libcore.io.BlockGuardOs.recvfrom(BlockGuardOs.java:163)
            at libcore.io.IoBridge.recvfrom(IoBridge.java:513)
            at java.net.PlainSocketImpl.read(PlainSocketImpl.java:488)
            at java.net.PlainSocketImpl.access$000(PlainSocketImpl.java:46)
            at java.net.PlainSocketImpl$PlainSocketInputStream.read(PlainSocketImpl.java:240)
            at java.io.InputStream.read(InputStream.java:163)
            at java.io.BufferedInputStream.fillbuf(BufferedInputStream.java:142)
            at java.io.BufferedInputStream.read(BufferedInputStream.java:227)
            at libcore.io.Streams.readAsciiLine(Streams.java:201)
            at libcore.net.http.ChunkedInputStream.readChunkSize(ChunkedInputStream.java:77)
            at libcore.net.http.ChunkedInputStream.read(ChunkedInputStream.java:68)
            at java.io.InputStream.read(InputStream.java:163)
            at java.util.zip.InflaterInputStream.fill(InflaterInputStream.java:200)
            at java.util.zip.InflaterInputStream.read(InflaterInputStream.java:154)
            at java.util.zip.GZIPInputStream.read(GZIPInputStream.java:167)
        ...
 *  permitCustomSlowCalls()、permitDiskReads ()、permitDiskWrites()、permitNetwork： 如果你想关闭某一项检测，可以使用对应的permit\*方法。

## VMPolicy 详解 ##

*  detectActivityLeaks() 用户检查 Activity 的内存泄露情况，比如下面的代码：

public class ActivityTestActivityLeaks extends Activity { 
        
        private static boolean isStrictMode = false;
        
        @Override
        protected void onCreate(Bundle savedInstanceState) { 
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_main);
    
            if(! isStrictMode){ 
                
                StrictMode.setVmPolicy(new VmPolicy.Builder()
                .detectActivityLeaks()
                .penaltyLog()
                .build());
                isStrictMode = true;
            }
            
            new Thread() { 
                  @Override
                  public void run() { 
                    while (true) { 
                        
                      SystemClock.sleep(1000);
                    }
                  }
            }.start();
        }
    }

我们反复旋转屏幕就会输出如下信息（重点在 instances=4; limit=1 这一行）：

...: E/StrictMode(4784): class com.ap.teststrictmode.ActivityTestActivityLeaks; instances=4; limit=1
    ...: E/StrictMode(4784): android.os.StrictMode$InstanceCountViolation: class com.ap.teststrictmode.ActivityTestActivityLeaks; instances=4; limit=1
    ...: E/StrictMode(4784):    at android.os.StrictMode.setClassInstanceLimit(StrictMode.java:1)

这时因为，我们在Activity中创建了一个Thread匿名内部类，而匿名内部类隐式持有外部类的引用。而每次旋转屏幕是，Android会新创建一个Activity，而原来的Activity实例又被我们启动的匿名内部类线程持有，所以不会释放，从日志上看，当先系统中该Activty有4个实例，而限制是只能创建1各实例。我们不断翻转屏幕，instances 的个数还会持续增加。

*  detectLeakedClosableObjects() 和 detectLeakedSqlLiteObjects()，资源没有正确关闭时回触发，比如下面的代码：

public class MainActivityTestDetectLeakedClosableObjects extends Activity { 
        
        private static boolean isStrictMode = false;
        
        @Override
        protected void onCreate(Bundle savedInstanceState) { 
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_main);
    
            
            if(! isStrictMode){ 
                StrictMode.setVmPolicy(new VmPolicy.Builder()
                .detectLeakedClosableObjects()
                .penaltyLog()
                .build());
                isStrictMode = true;
            }
            
            File newxmlfile = new File(Environment.getExternalStorageDirectory(), "aaa.txt");
            try { 
                newxmlfile.createNewFile();
                FileWriter fw = new FileWriter(newxmlfile);
                fw.write("aaaaaaaaaaa");
                //fw.close(); 我们在这里故意没有关闭 fw
            } catch (IOException e) { 
                e.printStackTrace();
            }
    
        }
    }

会产生如下异常信息：

... E/StrictMode(22056): A resource was acquired at attached stack trace but never released. See java.io.Closeable for information on avoiding resource leaks.
    ... E/StrictMode(22056): java.lang.Throwable: Explicit termination method 'close' not called
    ... E/StrictMode(22056):    at dalvik.system.CloseGuard.open(CloseGuard.java:184)
    ... E/StrictMode(22056):    at java.io.FileOutputStream.(FileOutputStream.java:90)
    ... E/StrictMode(22056):    at java.io.FileOutputStream.(FileOutputStream.java:73)
    ... E/StrictMode(22056):    at java.io.FileWriter.(FileWriter.java:42)
    ... E/StrictMode(22056):    at com.ap.teststrictmode.MainActivityTestDetectLeakedClosableObjects.onCreate(MainActivityTestDetectLeakedClosableObjects.java:44)
    ... E/StrictMode(22056):    at android.app.Activity.performCreate(Activity.java:5122)
    ... E/StrictMode(22056):    at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1081)
    ... E/StrictMode(22056):    at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2270)
    ... E/StrictMode(22056):    at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2358)
    ... E/StrictMode(22056):    at android.app.ActivityThread.handleRelaunchActivity(ActivityThread.java:3865)
    （后面的省略）

detectLeakedSqlLiteObjects() 和 detectLeakedClosableObjects()的用法类似，只不过是用来检查 SQLiteCursor 或者 其他 SQLite 对象是否被正确关闭。

*  detectLeakedRegistrationObjects() 用来检查 BroadcastReceiver 或者 ServiceConnection 注册类对象是否被正确释放，看下面的代码

public class ActivityTestLeakedRegistrationObjects extends Activity { 
        private TextView textView = null;
        private static boolean isStrictMode = false;
        private MyReceiver receiver = null;
        
        @Override
        protected void onCreate(Bundle savedInstanceState) { 
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_main);
    
            this.textView = (TextView) findViewById(R.id.text_view);
            
            this.textView.setText("In ActivityTestLeakedRegistrationObjects");
    
            
            if(! isStrictMode){ 
                StrictMode.setVmPolicy(new VmPolicy.Builder()
                .detectLeakedRegistrationObjects()
                .penaltyLog()
                .build());
                isStrictMode = true;
            }
            
            this.receiver = new MyReceiver();  
            IntentFilter filter = new IntentFilter();  
            filter.addAction("android.intent.action.MY_BROADCAST"); 
            registerReceiver(this.receiver, filter); 
        }
        
        @Override
        protected void onDestroy() { 
            super.onDestroy();
        }
    }

输入信息如下：

...: E/ActivityThread(24442): Activity com.ap.teststrictmode.ActivityTestLeakedRegistrationObjects has leaked IntentReceiver com.ap.teststrictmode.MyReceiver@41f1f128 that was originally registered here. Are you missing a call to unregisterReceiver()?
    ...: E/ActivityThread(24442): android.app.IntentReceiverLeaked: Activity com.ap.teststrictmode.ActivityTestLeakedRegistrationObjects has leaked IntentReceiver com.ap.teststrictmode.MyReceiver@41f1f128 that was originally registered here. Are you missing a call to unregisterReceiver()?
    ...: E/ActivityThread(24442):   at android.app.LoadedApk$ReceiverDispatcher.(LoadedApk.java:825)
    ...: E/ActivityThread(24442):   at android.app.LoadedApk.getReceiverDispatcher(LoadedApk.java:596)
    ...: E/ActivityThread(24442):   at android.app.ContextImpl.registerReceiverInternal(ContextImpl.java:1388)
    ...: E/ActivityThread(24442):   at android.app.ContextImpl.registerReceiver(ContextImpl.java:1368)
    ...

正确做法应该是在 onDestroy() 方法中将 receiver 释放掉：

@Override
        protected void onDestroy() { 
            unregisterReceiver(this.receiver);
            super.onDestroy();
        }

*  setClassInstanceLimit()，设置某个类的同时处于内存中的实例上限，可以协助检查内存泄露。比如下面的代码：

public class ActivityTestObjectLimit extends Activity { 
        private static class MyClass{}
        
        private static boolean isStrictMode = false;
        
        private static List<MyClass> classList = new ArrayList<ActivityTestObjectLimit.MyClass>();
        
        @Override
        protected void onCreate(Bundle savedInstanceState) { 
            super.onCreate(savedInstanceState);
            setContentView(R.layout.activity_main);
    
            if(! isStrictMode){ 
                StrictMode.setVmPolicy(new VmPolicy.Builder()
                .setClassInstanceLimit(MyClass.class, 2)
                .penaltyLog()
                .build());
                isStrictMode = true;
            }
            
            classList.add(new MyClass());
            classList.add(new MyClass());
            classList.add(new MyClass());
            classList.add(new MyClass());
            classList.add(new MyClass());
            classList.add(new MyClass());
            classList.add(new MyClass());
            classList.add(new MyClass());
        }
    }

日志信息如下：

...: E/StrictMode(27681): class com.ap.teststrictmode.ActivityTestObjectLimit$MyClass; instances=72; limit=2
    ...: E/StrictMode(27681): android.os.StrictMode$InstanceCountViolation: class com.ap.teststrictmode.ActivityTestObjectLimit$MyClass; instances=8; limit=2
    ...: E/StrictMode(27681):   at android.os.StrictMode.setClassInstanceLimit(StrictMode.java:1)

注意：上面的异常一般都在GC之后抛出，如果测试的时候没有现象，可以多翻转几次屏幕，或者通过DDMS工具手动触发一下。

[Android]: http://lib.csdn.net/base/15
[http_developer.android.com_reference_android_os_StrictMode.html]: http://developer.android.com/reference/android/os/StrictMode.html
[dialog.png]: http://android-performance.com/images/android-strict-mode/dialog.png
[ThreadPolicy]: http://developer.android.com/reference/android/os/StrictMode.ThreadPolicy.html
[VmPolicy]: http://developer.android.com/reference/android/os/StrictMode.VmPolicy.html
[StrictMode.ThreadPolicy.Builder]: http://developer.android.com/reference/android/os/StrictMode.ThreadPolicy.Builder.html