StrictMode  |  API reference  |  Android Developers (original) (raw)

public final class StrictMode
extends [Object](/reference/java/lang/Object) ``

StrictMode is a developer tool which detects things you might be doing by accident and brings them to your attention so you can fix them.

StrictMode is most commonly used to catch accidental disk or network access on the application's main thread, where UI operations are received and animations take place. Keeping disk and network operations off the main thread makes for much smoother, more responsive applications. By keeping your application's main thread responsive, you also prevent ANR dialogs from being shown to users.

Note that even though an Android device's disk is often on flash memory, many devices run a filesystem on top of that memory with very limited concurrency. It's often the case that almost all disk accesses are fast, but may in individual cases be dramatically slower when certain I/O is happening in the background from other processes. If possible, it's best to assume that such things are not fast.

Example code to enable from early in your [Application](/reference/android/app/Application), [Activity](/reference/android/app/Activity), or other application component's [Application.onCreate()](/reference/android/app/Application#onCreate%28%29) method:

override fun onCreate(savedInstanceState: Bundle?) { super.onCreate(savedInstanceState) StrictMode.setThreadPolicy( StrictMode.ThreadPolicy.Builder() .detectAll() .build() ) StrictMode.setVmPolicy( StrictMode.VmPolicy.Builder() .detectAll() .build() ) }

You can decide what should happen when a violation is detected. For example, using [ThreadPolicy.Builder.penaltyLog](/reference/android/os/StrictMode.ThreadPolicy.Builder#penaltyLog%28%29) you can watch the output of adb logcat while you use your application to see the violations as they happen.

If you find violations that you feel are problematic, there are a variety of tools to help solve them: threads, [Handler](/reference/android/os/Handler), [AsyncTask](/reference/android/os/AsyncTask), [IntentService](/reference/android/app/IntentService), etc. But don't feel compelled to fix everything that StrictMode finds. In particular, many cases of disk access are often necessary during the normal activity lifecycle. Use StrictMode to find things you did by accident. Network requests on the UI thread are almost always a problem, though.

StrictMode is not a security mechanism and is not guaranteed to find all disk or network accesses. While it does propagate its state across process boundaries when doing [Binder](/reference/android/os/Binder) calls, it's still ultimately a best effort mechanism. Notably, disk or network access from JNI calls won't necessarily trigger it.

Summary

Nested classes
interface StrictMode.OnThreadViolationListener When #ThreadPolicy.Builder.penaltyListener is enabled, the listener is called on the provided executor when a Thread violation occurs.
interface StrictMode.OnVmViolationListener When #VmPolicy.Builder.penaltyListener is enabled, the listener is called on the provided executor when a VM violation occurs.
class StrictMode.ThreadPolicy StrictMode policy applied to a certain thread.
class StrictMode.VmPolicy StrictMode policy applied to all threads in the virtual machine's process.
Public methods
staticStrictMode.ThreadPolicy allowThreadDiskReads() A convenience wrapper that takes the current ThreadPolicy from getThreadPolicy(), modifies it to permit disk reads, and sets the new policy with setThreadPolicy(ThreadPolicy), returning the old policy so you can restore it at the end of a block.
staticStrictMode.ThreadPolicy allowThreadDiskWrites() A convenience wrapper that takes the current ThreadPolicy from getThreadPolicy(), modifies it to permit both disk reads & writes, and sets the new policy with setThreadPolicy(ThreadPolicy), returning the old policy so you can restore it at the end of a block.
static void enableDefaults() Enables the recommended StrictMode defaults, with violations just being logged.
staticStrictMode.ThreadPolicy getThreadPolicy() Returns the current thread's policy.
staticStrictMode.VmPolicy getVmPolicy() Gets the current VM policy.
static void noteSlowCall(String name) For code to note that it's slow.
static void setThreadPolicy(StrictMode.ThreadPolicy policy) Sets the policy for what actions on the current thread should be detected, as well as the penalty if such actions occur.
static void setVmPolicy(StrictMode.VmPolicy policy) Sets the policy for what actions in the VM process (on any thread) should be detected, as well as the penalty if such actions occur.
Inherited methods
From class java.lang.Object Object clone() Creates and returns a copy of this object. boolean equals(Object obj) Indicates whether some other object is "equal to" this one. void finalize() Called by the garbage collector on an object when garbage collection determines that there are no more references to the object. finalClass<?> getClass() Returns the runtime class of this Object. int hashCode() Returns a hash code value for the object. final void notify() Wakes up a single thread that is waiting on this object's monitor. final void notifyAll() Wakes up all threads that are waiting on this object's monitor. String toString() Returns a string representation of the object. final void wait(long timeoutMillis, int nanos) Causes the current thread to wait until it is awakened, typically by being notified or interrupted, or until a certain amount of real time has elapsed. final void wait(long timeoutMillis) Causes the current thread to wait until it is awakened, typically by being notified or interrupted, or until a certain amount of real time has elapsed. final void wait() Causes the current thread to wait until it is awakened, typically by being notified or interrupted.

Public methods

enableDefaults

public static void enableDefaults ()

Enables the recommended StrictMode defaults, with violations just being logged.

This catches disk and network access on the main thread, as well as leaked SQLite cursors and unclosed resources. This is simply a wrapper around [setVmPolicy(VmPolicy)](/reference/android/os/StrictMode#setVmPolicy%28android.os.StrictMode.VmPolicy%29) and [setThreadPolicy(ThreadPolicy)](/reference/android/os/StrictMode#setThreadPolicy%28android.os.StrictMode.ThreadPolicy%29).

setThreadPolicy

public static void setThreadPolicy (StrictMode.ThreadPolicy policy)

Sets the policy for what actions on the current thread should be detected, as well as the penalty if such actions occur.

Internally this sets a thread-local variable which is propagated across cross-process IPC calls, meaning you can catch violations when a system service or another process accesses the disk or network on your behalf.

Parameters
policy StrictMode.ThreadPolicy: the policy to put into place

setVmPolicy

public static void setVmPolicy (StrictMode.VmPolicy policy)

Sets the policy for what actions in the VM process (on any thread) should be detected, as well as the penalty if such actions occur.

Parameters
policy StrictMode.VmPolicy: the policy to put into place