我添加了如下的traceview代码：
Debug.startMethodTracing("perf_trance");
//code
Debug.stopMethodTracing();
然后，我在清单中设置了所需的权限。
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />
但是当我运行我的应用程序以追溯性能时，我得到了RuntimeException：
06-04 14:57:23.083: E/AndroidRuntime(5584): java.lang.RuntimeException: Unable to start activity ComponentInfo{com.myxx.testapp/com.myxx.testapp.MainActivity}: java.lang.RuntimeException: Unable to open trace file '/mnt/sdcard/perf_trance.trace': Permission denied
06-04 14:57:23.083: E/AndroidRuntime(5584): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2007)
06-04 14:57:23.083: E/AndroidRuntime(5584): at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2034)
06-04 14:57:23.083: E/AndroidRuntime(5584): at android.app.ActivityThread.access$600(ActivityThread.java:129)
06-04 14:57:23.083: E/AndroidRuntime(5584): at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1185)
06-04 14:57:23.083: E/AndroidRuntime(5584): at android.os.Handler.dispatchMessage(SourceFile:99)
06-04 14:57:23.083: E/AndroidRuntime(5584): at android.os.Looper.loop(SourceFile:137)
06-04 14:57:23.083: E/AndroidRuntime(5584): at android.app.ActivityThread.main(ActivityThread.java:4518)
06-04 14:57:23.083: E/AndroidRuntime(5584): at java.lang.reflect.Method.invokeNative(Native Method)
06-04 14:57:23.083: E/AndroidRuntime(5584): at java.lang.reflect.Method.invoke(Method.java:511)
06-04 14:57:23.083: E/AndroidRuntime(5584): at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(SourceFile:809)
06-04 14:57:23.083: E/AndroidRuntime(5584): at com.android.internal.os.ZygoteInit.main(SourceFile:576)
06-04 14:57:23.083: E/AndroidRuntime(5584): at dalvik.system.NativeStart.main(Native Method)
06-04 14:57:23.083: E/AndroidRuntime(5584): Caused by: java.lang.RuntimeException: Unable to open trace file '/mnt/sdcard/perf_trance.trace': Permission denied
06-04 14:57:23.083: E/AndroidRuntime(5584): at dalvik.system.VMDebug.startMethodTracingNative(Native Method)
06-04 14:57:23.083: E/AndroidRuntime(5584): at dalvik.system.VMDebug.startMethodTracing(VMDebug.java:175)
06-04 14:57:23.083: E/AndroidRuntime(5584): at android.os.Debug.startMethodTracing(SourceFile:496)
06-04 14:57:23.083: E/AndroidRuntime(5584): at android.os.Debug.startMethodTracing(SourceFile:444)
06-04 14:57:23.083: E/AndroidRuntime(5584): at com.mediatek.oobe.basic.MainActivity.onCreate(MainActivity.java:154)
06-04 14:57:23.083: E/AndroidRuntime(5584): at android.app.Activity.performCreate(Activity.java:4479)
06-04 14:57:23.083: E/AndroidRuntime(5584): at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1050)
06-04 14:57:23.083: E/AndroidRuntime(5584): at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1971)
06-04 14:57:23.083: E/AndroidRuntime(5584): ... 11
我不知道为什么traceview无法写入/ mnt / sdcard /？
我还注意到目录的权限是d --- rwxr-x，这是根本原因吗？