一眠蚂、使用嚴(yán)格模式：

微信圖片_20180525114217.png

二读虏、嚴(yán)格模式中是如何去檢測(cè)，在哪個(gè)地方有注入StrictMode的代碼：
在源碼中可以直接植入StrictMode的檢查代碼袁滥、也可以植入代碼是BlockGuard和CloseGuard的代碼盖桥。
我們先看下UML：

2.png

public final class StrictMode {    
    public static void setThreadPolicy(final ThreadPolicy policy) {
        setThreadPolicyMask(policy.mask);
    }
    private static void setThreadPolicyMask(final int policyMask) {
        setBlockGuardPolicy(policyMask);
        Binder.setThreadStrictModePolicy(policyMask);
    }

    // Sets the policy in Dalvik/libcore (BlockGuard)
    private static void setBlockGuardPolicy(final int policyMask) {
        if (policyMask == 0) {
            BlockGuard.setThreadPolicy(BlockGuard.LAX_POLICY);
            return;
        }
        final BlockGuard.Policy policy = BlockGuard.getThreadPolicy();
        final AndroidBlockGuardPolicy androidPolicy;
        if (policy instanceof AndroidBlockGuardPolicy) {
            androidPolicy = (AndroidBlockGuardPolicy) policy;
        } else {
            androidPolicy = threadAndroidPolicy.get();
            BlockGuard.setThreadPolicy(androidPolicy);
        }
        androidPolicy.setPolicyMask(policyMask);
    }
}

其中在setBlockGuardPolicy(policyMask)把相應(yīng)的AndroidBlockGuardPolicy設(shè)置到BlockGuard類题翻，
并且Binder.setThreadStrictModePolicy()是Native層揩徊，當(dāng)進(jìn)程A發(fā)起跨進(jìn)程調(diào)用進(jìn)入到進(jìn)程B后，進(jìn)程B中的違規(guī)異常也是會(huì)通過Binder再傳回進(jìn)程A中嵌赠。
2塑荒、CloseGuard：

public final class StrictMode {    
    public static void setVmPolicy(final VmPolicy policy) {
        synchronized (StrictMode.class) {
            sVmPolicy = policy;
            sVmPolicyMask = policy.mask;
            setCloseGuardEnabled(vmClosableObjectLeaksEnabled());
            ...
        }
    }
    private static void setCloseGuardEnabled(boolean enabled) {
        if (!(CloseGuard.getReporter() instanceof AndroidCloseGuardReporter)) {
            CloseGuard.setReporter(new AndroidCloseGuardReporter());
        }
        CloseGuard.setEnabled(enabled);
    }
}

函數(shù)setCloseGuardEnabled注入AndroidCloseGuardReporter后，在Android很多代碼都會(huì)使用CloseGuard.get()獲取全局的CloseGuard進(jìn)行檢測(cè)輸出打印日志出來猾普。
三袜炕、植入嚴(yán)格模式檢測(cè)的代碼：
1）、FileInPutStream中：讀寫file時(shí)初家，有BlockGuard檢測(cè)UI線程操作文件偎窘，有CloseGuard檢測(cè)報(bào)告的未關(guān)閉文件等。

class FileInputStream extends InputStream{
    private final CloseGuard guard = CloseGuard.get();
     public FileInputStream(File file) throws FileNotFoundException {
        ...
        BlockGuard.getThreadPolicy().onReadFromDisk();
        open(name);
        guard.open("close");
    }
    public void close() throws IOException {
        ...
        guard.close();
        ...
    }
    protected void finalize() throws IOException {
        if (guard != null) {
            guard.warnIfOpen();
        }
        if ((fd != null) &&  (fd != FileDescriptor.in)) {
            close();
        }
    }
}

2）溜在、SQLiteCursor ：在SQLiteCursor對(duì)象銷毀時(shí)陌知，會(huì)對(duì)Cursor是否關(guān)閉進(jìn)行判斷相應(yīng)向StrictMode報(bào)告

public class SQLiteCursor extends AbstractWindowedCursor {
     public SQLiteCursor(SQLiteCursorDriver driver, String editTable, SQLiteQuery query) {
        ...
        if (StrictMode.vmSqliteObjectLeaksEnabled()) {
            mStackTrace = new DatabaseObjectNotClosedException().fillInStackTrace();
        } else {
            mStackTrace = null;
        }
        ...
    }
    protected void finalize() {
        try {
            if (mWindow != null) {
                if (mStackTrace != null) {
                    String sql = mQuery.getSql();
                    int len = sql.length();
                    StrictMode.onSqliteObjectLeaked(
                        "Finalizing a Cursor that has not been deactivated or closed. " +
                        "database = " + mQuery.getDatabase().getLabel() +
                        ", table = " + mEditTable +
                        ", query = " + sql.substring(0, (len > 1000) ? 1000 : len),
                        mStackTrace);
                }
                close();
            }
        } finally {
            super.finalize();
        }
    }
}

3）、Activity泄露掖肋，在ActivityThread中Activity的啟動(dòng)和銷毀都有植入StrictMode相應(yīng)的代碼去檢測(cè)Activity的引用計(jì)數(shù)仆葡，來判斷是否有泄露，在StrictMode.decrementExpectedActivityCount(activityClass);會(huì)手動(dòng)System.gc();

public final class ActivityThread {
    private Activity performLaunchActivity(ActivityClientRecord r, Intent customIntent) {
        ...
        Activity activity = null;
        try {
            java.lang.ClassLoader cl = r.packageInfo.getClassLoader();
            activity = mInstrumentation.newActivity(
                    cl, component.getClassName(), r.intent);
            StrictMode.incrementExpectedActivityCount(activity.getClass());
            ...
        } catch (Exception e) {
        }
       ...
       return activity;
    }
    private ActivityClientRecord performDestroyActivity(IBinder token, boolean finishing,
            int configChanges, boolean getNonConfigInstance) {
            ...
            try {
                r.activity.mCalled = false;
                mInstrumentation.callActivityOnDestroy(r.activity);
                ...
            } catch (Exception e) {      
                }
            }
        StrictMode.decrementExpectedActivityCount(activityClass);
        return r;
    }
}

4）志笼、SharedPreferencesImpl 中g(shù)etString沿盅、getInt等也植入了BlockGuard

final class SharedPreferencesImpl implements SharedPreferences {
    @Nullable
    public String getString(String key, @Nullable String defValue) {
        synchronized (this) {
            awaitLoadedLocked();
            ...
        }
    }

    @Nullable
    public Set<String> getStringSet(String key, @Nullable Set<String> defValues) {
        synchronized (this) {
            awaitLoadedLocked();
            ...
        }
    }

    public int getInt(String key, int defValue) {
        synchronized (this) {
            awaitLoadedLocked();
            ...
        }
    }
    private void awaitLoadedLocked() {
        if (!mLoaded) {
            // Raise an explicit StrictMode onReadFromDisk for this
            // thread, since the real read will be in a different
            // thread and otherwise ignored by StrictMode.
            BlockGuard.getThreadPolicy().onReadFromDisk();
        }
        while (!mLoaded) {
            try {
                wait();
            } catch (InterruptedException unused) {
            }
        }
    }
}