StrictMode最常用來捕捉應用程序的主線程，它將報告與線程及虛擬機相關的策略違例。一旦檢測到策略違例（policy violation），你將獲得警告，其包含了一個棧trace顯示你的應用在何處發生違例。除了主線程，我們還可以在Handler，AsyncTask，AsyncQueryHandler，IntentService等API中使用StrictMode。
StrictMode的線程策略主要用於檢測磁盤IO和網絡訪問，而虛擬機策略主要用於檢測內存洩漏現象。Android已經在磁盤IO訪問和網絡訪問的代碼中已經加入了StrictMode。當監視的線程發生策略的違例時，就可以獲得警告，例如寫入LogCat，顯示一個對話框，閃下屏幕，寫入DropBox日志文件，或讓應用崩潰。最通常的做法是寫入LogCat或讓應用崩潰。下面的代碼展示了如何使用StrictMode的檢查策略：
public void onCreate() {
if (DEVELOPER_MODE) {
StrictMode.setThreadPolicy(new StrictMode.ThreadPolicy.Builder()
.detectDiskReads()
.detectDiskWrites()
.penaltyDialog()
.detectNetwork() // or .detectAll() for all detectable problems
.penaltyLog()
.build());
StrictMode.setVmPolicy(new StrictMode.VmPolicy.Builder()
.detectLeakedSqlLiteObjects()
.detectLeakedClosableObjects()
.penaltyLog()
.penaltyDeath()
.build());
}
super.onCreate();
}
如果不指定檢測函數，也可以用detectAll()來替代。penaltyLog()表示將警告輸出到LogCat，你也可以使用其他或增加新的懲罰（penalty）函數，例如使用penaltyDeath()的話，一旦StrictMode消息被寫到LogCat後應用就會崩潰。
在正式版本中，我們並不希望使用StrictMode來讓用戶的應用因為一個警告而崩潰，所以在應用正式發布時，需要移出這些監視。你可以通過刪除代碼來實現，不過這裡提供一個更好的方式來解決這個問題，即使用AndroidMainifest文件中的debuggable屬性來實現，代碼如下所示：
android:debuggable=true
在代碼中，使用方法如下所示：
// Return if this application is not in debug mode
ApplicationInfo appInfo = context.getApplicationInfo();
int appFlags = appInfo.flags;
if ((appFlags & ApplicationInfo.FLAG_DEBUGGABLE) != 0) {
// Do StrictMode setup here
StrictMode.setVmPolicy(new StrictMode.VmPolicy.Builder()
.detectLeakedSqlLiteObjects()
.penaltyLog()
.penaltyDeath()
.build());
}
我們在測試代碼的主線程中去訪問網絡，這樣就一定會觸發StrictMode的線程監測，代碼如下所示：
public class MainActivity extends Activity {
private HttpResponse httpResponse = null;
private HttpEntity httpEntity = null;
private TextView mTextView;
@Override
protected void onCreate(Bundle savedInstanceState) {
StrictMode.setThreadPolicy(new StrictMode.ThreadPolicy.Builder()
.detectDiskReads()
.detectDiskWrites()
.detectNetwork()
.penaltyDialog()
.penaltyLog()
.build());
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
mTextView = (TextView) findViewById(R.id.text);
HttpGet httpGet = new HttpGet(http://www.baidu.com);
HttpClient httpClient = new DefaultHttpClient();
InputStream inputStream = null;
try {
httpResponse = httpClient.execute(httpGet);
httpEntity = httpResponse.getEntity();
if (httpResponse.getStatusLine().getStatusCode() == 200) {
inputStream = httpEntity.getContent();
BufferedReader reader =
new BufferedReader(new InputStreamReader(inputStream));
mTextView.setText(reader.readLine());
}
} catch (Exception e) {
e.printStackTrace();
} finally {
try {
inputStream.close();
} catch (IOException e) {
e.printStackTrace();
}
}
}
}
運行代碼，並將Log信息保存到本地，在Log中，我們可以搜索D/StrictMode(15454): StrictMode policy violation關鍵字。這裡截取一段，如下所示：
D/StrictMode(15454): StrictMode policy violation; ~duration=461 ms: android.os.StrictMode$StrictModeNetworkViolation: policy=55 violation=4 D/StrictMode(15454): at android.os.StrictMode$AndroidBlockGuardPolicy.onNetwork(StrictMode.java:1153) D/StrictMode(15454): at libcore.io.BlockGuardOs.recvfrom(BlockGuardOs.java:249) D/StrictMode(15454): at libcore.io.IoBridge.recvfrom(IoBridge.java:553) D/StrictMode(15454): at java.net.PlainSocketImpl.read(PlainSocketImpl.java:485) D/StrictMode(15454): at java.net.PlainSocketImpl.access$000(PlainSocketImpl.java:37) D/StrictMode(15454): at java.net.PlainSocketImpl$PlainSocketInputStream.read(PlainSocketImpl.java:237) D/StrictMode(15454): at org.apache.http.impl.io.AbstractSessionInputBuffer.fillBuffer(AbstractSessionInputBuffer.java:103) D/StrictMode(15454): at org.apache.http.impl.io.AbstractSessionInputBuffer.read(AbstractSessionInputBuffer.java:134) D/StrictMode(15454): at org.apache.http.impl.io.ChunkedInputStream.read(ChunkedInputStream.java:161) D/StrictMode(15454): at org.apache.http.impl.io.ChunkedInputStream.read(ChunkedInputStream.java:175) D/StrictMode(15454): at org.apache.http.impl.io.ChunkedInputStream.exhaustInputStream(ChunkedInputStream.java:289) D/StrictMode(15454): at org.apache.http.impl.io.ChunkedInputStream.close(ChunkedInputStream.java:262) D/StrictMode(15454): at org.apache.http.conn.BasicManagedEntity.streamClosed(BasicManagedEntity.java:179) D/StrictMode(15454): at org.apache.http.conn.EofSensorInputStream.checkClose(EofSensorInputStream.java:266) D/StrictMode(15454): at org.apache.http.conn.EofSensorInputStream.close(EofSensorInputStream.java:213) D/StrictMode(15454): at com.imooc.strictmodetest.MainActivity.onCreate(MainActivity.java:53) D/StrictMode(15454): at android.app.Activity.performCreate(Activity.java:5976) D/StrictMode(15454): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1105) D/StrictMode(15454): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2262) D/StrictMode(15454): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2371) D/StrictMode(15454): at android.app.ActivityThread.access$800(ActivityThread.java:149) D/StrictMode(15454): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1289) D/StrictMode(15454): at android.os.Handler.dispatchMessage(Handler.java:102) D/StrictMode(15454): at android.os.Looper.loop(Looper.java:135) D/StrictMode(15454): at android.app.ActivityThread.main(ActivityThread.java:5260) D/StrictMode(15454): at java.lang.reflect.Method.invoke(Native Method) D/StrictMode(15454): at java.lang.reflect.Method.invoke(Method.java:372) D/StrictMode(15454): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:898) D/StrictMode(15454): at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:693)
Log中可以顯示出StrictMode提示的原因，通過這裡的TraceLog我們就可以來找到優化的方法。除了在Logcat中查看StrictMode的日志信息，如果你使用了penaltyDropbox()方法，那麼你還可以通過如下所示的命令來調用DropBoxManager觀察StrictMode日志：
adb shell dumpsys dropbox data_app_strictmode --print
輸出日志文件如下所示：
======================================== 2015-03-09 17:47:14 data_app_strictmode (text, 2177 bytes) Process: com.imooc.strictmodetest Flags: 0x88be46 Package: com.imooc.strictmodetest v1 (1.0) Build: TCL/idol347/idol347:5.0.2/LRX22G/1040:userdebug/release-keys System-App: false Uptime-Millis: 389545133 Loop-Violation-Number: 4 Duration-Millis: 520 android.os.StrictMode$StrictModeNetworkViolation: policy=183 violation=4 at android.os.StrictMode$AndroidBlockGuardPolicy.onNetwork(StrictMode.java:1153) at java.net.InetAddress.lookupHostByName(InetAddress.java:418) at java.net.InetAddress.getAllByNameImpl(InetAddress.java:252) at java.net.InetAddress.getAllByName(InetAddress.java:215) at org.apache.http.impl.conn.DefaultClientConnectionOperator.openConnection(DefaultClientConnectionOperator.java:137) at org.apache.http.impl.conn.AbstractPoolEntry.open(AbstractPoolEntry.java:164) at org.apache.http.impl.conn.AbstractPooledConnAdapter.open(AbstractPooledConnAdapter.java:119) at org.apache.http.impl.client.DefaultRequestDirector.execute(DefaultRequestDirector.java:360) at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:555) at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:487) at org.apache.http.impl.client.AbstractHttpClient.execute(AbstractHttpClient.java:465) at com.imooc.strictmodetest.MainActivity.onCreate(MainActivity.java:43) at android.app.Activity.performCreate(Activity.java:5976) at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1105) at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2262) at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2371) at android.app.ActivityThread.access$800(ActivityThread.java:149) at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1289) at android.os.Handler.dispatchMessage(Handler.java:102) at android.os.Looper.loop(Looper.java:135) at android.app.ActivityThread.main(ActivityThread.java:5260) at java.lang.reflect.Method.invoke(Native Method) at java.lang.reflect.Method.invoke(Method.java:372) at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:898) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:693)
同時，如果使用了penaltyDialog()方法，在應用中還會彈出 提示框：
StrictMode.ThreadPolicy old = StrictMode.getThreadPolicy();
StrictMode.setThreadPolicy(new StrictMode.ThreadPolicy.Builder(old)
.permitDiskWrites()
.build());
//doSomethingWriteToDisk();
StrictMode.setThreadPolicy(old);
