Create DefaultUncaughtExceptionHandler.md

Author: android-notes

DefaultUncaughtExceptionHandler.md

@@ -0,0 +1,107 @@
+`Thread.setDefaultUncaughtExceptionHandler`
+
+```java
+
+public class MainActivity extends AppCompatActivity {
+    @Override
+    protected void onCreate(Bundle savedInstanceState) {
+        super.onCreate(savedInstanceState);
+        setContentView(R.layout.activity_main);
+
+        final Thread.UncaughtExceptionHandler uncaughtExceptionHandler=Thread.getDefaultUncaughtExceptionHandler();
+        Thread.setDefaultUncaughtExceptionHandler(new Thread.UncaughtExceptionHandler() {
+            @Override
+            public void uncaughtException(Thread t, Throwable e) {
+                Log.e("AndroidRuntime","--->uncaughtException:"+t+"<---",e);
+                uncaughtExceptionHandler.uncaughtException(t,e);//若不把异常交给默认的异常处理器处理会导致ANR，交给了就会导致crash
+            }
+        });
+
+
+        findViewById(R.id.but1).setOnClickListener(new View.OnClickListener() {
+            @Override
+            public void onClick(View v) {
+                throw new RuntimeException("click exception...");
+            }
+        });
+
+        findViewById(R.id.but2).setOnClickListener(new View.OnClickListener() {
+            @Override
+            public void onClick(View v) {
+                new Handler().post(new Runnable() {
+                    @Override
+                    public void run() {
+                        throw new RuntimeException("handler exception...");
+                    }
+                });
+            }
+        });
+
+        findViewById(R.id.but3).setOnClickListener(new View.OnClickListener() {
+            @Override
+            public void onClick(View v) {
+                new Thread() {
+                    @Override
+                    public void run() {
+                        super.run();
+                        throw new RuntimeException("new thread exception...");
+                    }
+                }.start();
+            }
+        });
+
+    }
+}
+
+```
+
+
+可以看到主线程的异常被UncaughtExceptionHandler捕获到了，若不把异常交给默认的异常处理器处理会导致ANR，交给了就会导致crash
+            
+```java
+
+02-17 09:36:00.152 19525-19525/wj.com.fuck E/AndroidRuntime: --->uncaughtException:Thread[main,5,main]<---
+                                                             java.lang.RuntimeException: click exception...
+                                                                 at wj.com.fuck.MainActivity$2.onClick(MainActivity.java:46)
+                                                                 at android.view.View.performClick(View.java:4909)
+                                                                 at android.view.View$PerformClick.run(View.java:20390)
+                                                                 at android.os.Handler.handleCallback(Handler.java:815)
+                                                                 at android.os.Handler.dispatchMessage(Handler.java:104)
+                                                                 at android.os.Looper.loop(Looper.java:194)
+                                                                 at android.app.ActivityThread.main(ActivityThread.java:5826)
+                                                                 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:1009)
+                                                                 at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:804)
+02-17 09:36:00.152 19525-19525/wj.com.fuck E/AndroidRuntime: FATAL EXCEPTION: main
+                                                             Process: wj.com.fuck, PID: 19525
+                                                             java.lang.RuntimeException: click exception...
+                                                                 at wj.com.fuck.MainActivity$2.onClick(MainActivity.java:46)
+                                                                 at android.view.View.performClick(View.java:4909)
+                                                                 at android.view.View$PerformClick.run(View.java:20390)
+                                                                 at android.os.Handler.handleCallback(Handler.java:815)
+                                                                 at android.os.Handler.dispatchMessage(Handler.java:104)
+                                                                 at android.os.Looper.loop(Looper.java:194)
+                                                                 at android.app.ActivityThread.main(ActivityThread.java:5826)
+                                                                 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:1009)
+                                                                 at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:804)
+
+```
+ 
+ 
+子线程抛出异常也可以被UncaughtExceptionHandler捕获到，即使不把异常交给默认的异常处理器处理也不会导致crash
+
+```java
+
+02-17 09:38:21.555 20825-20933/wj.com.fuck E/AndroidRuntime: --->uncaughtException:Thread[Thread-28481,5,main]<---
+                                                             java.lang.RuntimeException: new thread exception...
+                                                                 at wj.com.fuck.MainActivity$4$1.run(MainActivity.java:69)
+02-17 09:38:21.555 20825-20933/wj.com.fuck E/AndroidRuntime: FATAL EXCEPTION: Thread-28481
+                                                             Process: wj.com.fuck, PID: 20825
+                                                             java.lang.RuntimeException: new thread exception...
+                                                                 at wj.com.fuck.MainActivity$4$1.run(MainActivity.java:69)
+
+
+```