jint Throw(JNIEnv *env, jthrowable obj);
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Causes a java.lang.Throwable object to be thrown.

LINKAGE:

Index 13 in the JNIEnv interface function table.

PARAMETERS:

Env: JNI interface pointer.

Obj: a java.lang.Throwable object.

RETURNS:

Returns 0 on success; Negative on failure.

THROWS:

Java.lang.Throwable object obj.

jthrowable ExceptionOccurred(JNIEnv *env);
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Determines whether an exception is thrown. Exceptions are thrown until the native code calls ExceptionClear() or Java code handles the exception.

LINKAGE:

Index 15 in the JNIEnv interface function table.

PARAMETERS:

Env: JNI interface pointer.

RETURNS:

Returns the exception object currently being thrown, or NULL if no exception is currently being thrown.

void ExceptionClear(JNIEnv *env);
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Clears any exceptions that are currently being thrown. This routine is invalid if no exception is currently thrown.

LINKAGE:

Index 17 in the JNIEnv interface function table.

PARAMETERS:

Env: JNI interface pointer.

We introduced a convenience function to check for pending exceptions without creating a local reference to the exception object.

jboolean ExceptionCheck(JNIEnv *env);
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Return JNI_TRUE if there is a pending exception; Otherwise, JNI_FALSE is returned.

LINKAGE:

Index 228 in the JNIEnv interface function table.

SINCE:

The JDK/JRE 1.2

The divZero() method in Java code throws a ArithmeticException since the divisor is zero. The functions mentioned in the API are used in JNI to handle and throw exceptions, respectively. Practice the various JNI functions.

package ndk.example.com.ndkexample; import android.os.Bundle; import android.support.v7.app.AppCompatActivity; import android.widget.TextView; public class MainActivity extends AppCompatActivity { private static final String TAG = "Main"; static { System.loadLibrary("native-lib"); } @Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main); TextView tv = findViewById(R.id.sample_text); Tv.settext ("JNI exception handling...") ); nativeDiv(); //nativeThrowException(); //nativeFatalError(); } private void divZero() { int i = 5 / 0; } public native void nativeDiv(); public native void nativeThrowException(); public native void nativeFatalError(); }Copy the code

Native code:

#include <jni.h> #include <stdio.h> #include <android/log.h> #define TAG "Native" #define LOGI(...) ((void)__android_log_print(ANDROID_LOG_INFO, TAG, __VA_ARGS__)) #define LOGE(...) ((void)__android_log_print(ANDROID_LOG_ERROR, TAG, __VA_ARGS__)) extern "C" { JNIEXPORT void JNICALL Java_ndk_example_com_ndkexample_MainActivity_nativeDiv(JNIEnv *env, jobject instance) { jclass clz = env->GetObjectClass(instance); if (NULL == clz) { return; } jmethodID divMid = env->GetMethodID(clz, "divZero", "()V"); if (NULL == divMid) { return; } env->CallVoidMethod(instance, divMid); // Determine whether an exception is thrown. ExceptionClear() jthrowable jthrow = env->ExceptionOccurred(); ExceptionCheck() checks for exceptions. If exceptions occur, return JNI_TRUE. Otherwise return JNI_FALSE if (jthrow && env->ExceptionCheck()) {env->ExceptionDescribe(); // Prints stack exceptions and tracebacks to the system error reporting channel, such as stderr. This is a convenience routine for debugging. env->ExceptionClear(); // Clears any exceptions that are currently being thrown. This routine is invalid if no exception is currently thrown. LOGI("Run Java method find exception."); } jclass arithmeticExceptionCls = env->FindClass("java/lang/ArithmeticException"); if (NULL ! = arithmeticExceptionCls) {construct an exception object from the specified class using the specified message, Env ->ThrowNew(arithmeticExceptionCls, "Throw New Exception: divide by zero"); } LOGI("Run After JNI Throw New Exception."); } JNIEXPORT void JNICALL Java_ndk_example_com_ndkexample_MainActivity_nativeThrowException(JNIEnv *env, jobject) { jclass arithmeticExceptionCls = env->FindClass("java/lang/ArithmeticException"); if (NULL == arithmeticExceptionCls) { return; } jmethodID initMethodID = (env)->GetMethodID(arithmeticExceptionCls, "<init>", "(Ljava/lang/String;) V"); if (NULL == initMethodID) { return; } char infoBuf[256] = {0}; sprintf(infoBuf, "Exception from native."); jstring info = (env)->NewStringUTF(infoBuf); jthrowable thr = (jthrowable) (env)->NewObject(arithmeticExceptionCls, initMethodID, info); Env ->Throw(THR); } JNIEXPORT void JNICALL Java_ndk_example_com_ndkexample_MainActivity_nativeFatalError(JNIEnv *env, jobject) {// Raise fatal error, And you don't want the VM to recover. Env ->FatalError("FatalError MSG."); }}Copy the code

Native code uses throws and ThrowNew to Throw exceptions. The difference is that the Throw method takes jthrowable as an argument, whereas ThrowNew takes a java.lang.Throwable subclass and the message used to construct the java.lang.Throwable object as arguments. FatalError raises a FatalError and does not expect the VM to recover. This function does not return.

Uncomment the nativeThrowException() method in the routine and run the result again as follows:

10-26 10:11:06. 618 11967-11967 /ndk.example.com.ndkexample D/AndroidRuntime: Shutting down the VM -- -- -- -- -- -- -- -- -- beginning of crash 10-26 10:11:06. 619 11967-11967 /ndk.example.com.ndkexample E/AndroidRuntime: FATAL EXCEPTION: main Process: ndk.example.com.ndkexample, PID: 11967 java.lang.RuntimeException: Unable to start activity ComponentInfo{ndk.example.com.ndkexample/ndk.example.com.ndkexample.MainActivity}: java.lang.ArithmeticException: Exception from native. at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2339) at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2413) at android.app.ActivityThread.access$800(ActivityThread.java:155) at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1317) at android.os.Handler.dispatchMessage(Handler.java:102) at android.os.Looper.loop(Looper.java:135) at android.app.ActivityThread.main(ActivityThread.java:5343) 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:907) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:702) Caused by: java.lang.ArithmeticException: Exception from native. at ndk.example.com.ndkexample.MainActivity.nativeThrowException(Native Method) at ndk.example.com.ndkexample.MainActivity.onCreate(MainActivity.java:23) at android.app.Activity.performCreate(Activity.java:6010) at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1129) at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2292) at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2413) at android.app.ActivityThread.access$800(ActivityThread.java:155) at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1317) at android.os.Handler.dispatchMessage(Handler.java:102) at android.os.Looper.loop(Looper.java:135) at android.app.ActivityThread.main(ActivityThread.java:5343) 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:907) at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:702)Copy the code

The above results see Exception from native. This message is thrown by the Throw method.

Finally, open the nativeFatalError() comment and look at the result:

10-26 10:16:11. 770 12954-12954 /ndk.example.com.ndkexample A/art: art/runtime/jni_internal.cc:769] JNI FatalError called: FatalError MSG. 10-26 10:16:11. 925 12954-12954 /ndk.example.com.ndkexample A/art: art/runtime/runtime.cc:314] Runtime aborting... art/runtime/runtime.cc:314] Aborting thread: art/runtime/runtime.cc:314] "main" prio=5 tid=1 Runnable art/runtime/runtime.cc:314] | group="" sCount=0 dsCount=0 obj=0x73cddfa8 self=0x7f7e495000 art/runtime/runtime.cc:314] | sysTid=12954 nice=0 cgrp=apps sched=0/0 handle=0x7f8212fea0 art/runtime/runtime.cc:314] | state=R schedstat=( 90633388 7482185 83 ) utm=7 stm=2 core=5 HZ=100 art/runtime/runtime.cc:314] | stack=0x7fc0145000-0x7fc0147000 stackSize=8MB art/runtime/runtime.cc:314] | held mutexes= "abort lock" "mutator lock"(shared held) art/runtime/runtime.cc:314] native: #00 pc 000040f4 /system/lib64/libbacktrace_libc++.so (_ZN9Backtrace6UnwindEmP8ucontext+28) art/runtime/runtime.cc:314] native: #01 pc 0000001c ??? art/runtime/runtime.cc:314] at ndk.example.com.ndkexample.MainActivity.nativeFatalError(Native method) art/runtime/runtime.cc:314] at ndk.example.com.ndkexample.MainActivity.onCreate(MainActivity.java:24) art/runtime/runtime.cc:314] at android.app.Activity.performCreate(Activity.java:6010) art/runtime/runtime.cc:314] at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1129) art/runtime/runtime.cc:314] at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2292) art/runtime/runtime.cc:314] at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2413) art/runtime/runtime.cc:314] at android.app.ActivityThread.access$800(ActivityThread.java:155) art/runtime/runtime.cc:314] at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1317) art/runtime/runtime.cc:314] at android.os.Handler.dispatchMessage(Handler.java:102) art/runtime/runtime.cc:314] at android.os.Looper.loop(Looper.java:135) art/runtime/runtime.cc:314] at android.app.ActivityThread.main(ActivityThread.java:5343) art/runtime/runtime.cc:314] at java.lang.reflect.Method.invoke! (Native method) art/runtime/runtime.cc:314] at java.lang.reflect.Method.invoke(Method.java:372) art/runtime/runtime.cc:314] at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:907) art/runtime/runtime.cc:314] at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:702) art/runtime/runtime.cc:314] Dumping all threads without appropriate locks held: thread list lock art/runtime/runtime.cc:314] All threads: ...... art/runtime/runtime.cc:314] "Binder_2" prio=5 tid=15 Native art/runtime/runtime.cc:314] | group="" sCount=0 dsCount=0 obj=0x12c830a0 self=0x7f7e4a4000 art/runtime/runtime.cc:314] | sysTid=12973 nice=0 cgrp=apps sched=0/0 handle=0x7f77025300 art/runtime/runtime.cc:314] | state=S schedstat=( 718855 171043 3 ) utm=0 stm=0 core=2 HZ=100 art/runtime/runtime.cc:314] | stack=0x7f77b20000-0x7f77b22000 stackSize=1012KB art/runtime/runtime.cc:314] | held mutexes= art/runtime/runtime.cc:314] kernel: __switch_to+0x70/0x7c art/runtime/runtime.cc:314] kernel: binder_thread_read+0xd8c/0xecc art/runtime/runtime.cc:314] kernel: binder_ioctl+0x3f8/0x824 art/runtime/runtime.cc:314] kernel: do_vfs_ioctl+0x4a4/0x578 art/runtime/runtime.cc:314] kernel: SyS_ioctl+0x5c/0x88 art/runtime/runtime.cc:314] kernel: cpu_switch_to+0x48/0x4c art/runtime/runtime.cc:314] native: #00 pc 0006227c /system/lib64/libc.so (__ioctl+4) art/runtime/runtime.cc:314] native: #01 pc 0008a0dc /system/lib64/libc.so (ioctl+100) art/runtime/runtime.cc:314] native: #02 pc 0002de1c /system/lib64/libbinder.so (_ZN7android14IPCThreadState14talkWithDriverEb+164) art/runtime/runtime.cc:314] native: #03 pc 0002e690 /system/lib64/libbinder.so (_ZN7android14IPCThreadState20getAndExecuteCommandEv+24) art/runtime/runtime.cc:314] native: #04 pc 0002e748 /system/lib64/libbinder.so (_ZN7android14IPCThreadState14joinThreadPoolEb+76) art/runtime/runtime.cc:314] native: #05 pc 000360ec /system/lib64/libbinder.so (???) art/runtime/runtime.cc:314] native: #06 pc 00016a68 /system/lib64/libutils.so (_ZN7android6Thread11_threadLoopEPv+208) art/runtime/runtime.cc:314] native: #07 pc 00090454 /system/lib64/libandroid_runtime.so (_ZN7android14AndroidRuntime15javaThreadShellEPv+96) art/runtime/runtime.cc:314] native: #08 pc 0001647c /system/lib64/libutils.so (???) art/runtime/runtime.cc:314] native: #09 pc 0001f5c4 /system/lib64/libc.so (_ZL15__pthread_startPv+52) art/runtime/runtime.cc:314] native: #10 pc 0001b7b0 /system/lib64/libc.so (__start_thread+16) art/runtime/runtime.cc:314] (no managed stack frames) art/runtime/runtime.cc:314] art/runtime/runtime.cc:314]Copy the code

The consequences look worse than the last few! After all, FatalError raises fatal errors and does not want the VM to recover, so use it with caution.