Android 通过Application捕获全局异常，防止程序崩溃退出

因为要对全局进行一个“监听”，因此我们可以把一个监听异常的方法放在Applcation中，而它的生命周期也就是整个app的生命周期。

我们写一个类实现UncaughtExceptionHandler接口，这个接口是为了捕获没有被捕获的异常，包括运行时异常。

CrashHandler类：

package com.xiaoqi.crashhandlerdemo;

import java.io.FileOutputStream;
import java.io.IOException;
import java.io.PrintWriter;
import java.io.StringWriter;
import java.io.Writer;
import java.lang.Thread.UncaughtExceptionHandler;
import java.lang.reflect.Field;
import java.text.DateFormat;
import java.text.SimpleDateFormat;
import java.util.Date;
import java.util.HashMap;
import java.util.Map;

import android.content.Context;
import android.content.pm.PackageInfo;
import android.content.pm.PackageManager;
import android.content.pm.PackageManager.NameNotFoundException;
import android.os.Build;
import android.os.Environment;
import android.os.Looper;
import android.widget.Toast;

/*
 * 处理异常
 */
public class CrashHandler implements UncaughtExceptionHandler {
	Context mcontext;
	// 用来存储设备信息和异常信息
	private Map infos = new HashMap();
	// 获取系统默认的UncaughtException处理类
	private Thread.UncaughtExceptionHandler mDefaultHandler;
	// 用于格式化日期,作为日志文件名的一部分
	private DateFormat formatter = new SimpleDateFormat("yyyy-MM-dd-HH-mm-ss");
	// CrashHandler实例
	private static CrashHandler INSTANCE;

	public void init(Context context) {
		mcontext = context;
		mDefaultHandler = Thread.getDefaultUncaughtExceptionHandler();
		Thread.setDefaultUncaughtExceptionHandler(this);
	}

	/**
	 * 自定义错误处理，收集错误信息，发送错误报告等
	 * 
	 * @param ex
	 * @return
	 */
	private boolean handleException(Throwable ex) {
		if (ex == null) {
			return false;
		}
		new Thread() {
			public void run() {
				Looper.prepare();
				Toast.makeText(mcontext, "很抱歉,程序出现异常,即将退出.", Toast.LENGTH_LONG)
						.show();
				Looper.loop();
			};
		}.start();
		collectDeviceInfo(mcontext);
		saveCrashInfo2File(ex);
		return true;
	}

	/**
	 * 获取设备参数信息
	 * 
	 * @param context
	 */
	public void collectDeviceInfo(Context context) {
		PackageManager pm = context.getPackageManager();
		try {
			PackageInfo pi = pm.getPackageInfo(context.getPackageName(),
					PackageManager.GET_ACTIVITIES);
			if (pi != null) {
				String versionName = pi.versionName == null ? "null"
						: pi.versionName;
				String versionCode = pi.versionCode + "";
				infos.put("versionName", versionName);
				infos.put("versionCode", versionCode);
			}
		} catch (NameNotFoundException e) {
			// TODO Auto-generated catch block
			e.printStackTrace();
		}
		Field[] fields = Build.class.getDeclaredFields();
		for (Field field : fields) {
			field.setAccessible(true);
			try {
				infos.put(field.getName(), field.get(null).toString());
			} catch (IllegalAccessException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			} catch (IllegalArgumentException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			}
		}

	}

	private String saveCrashInfo2File(Throwable ex) {
		StringBuffer sb = new StringBuffer();
		for (Map.Entry entry : infos.entrySet()) {
			String key = entry.getKey();
			String value = entry.getValue();
			sb.append(key + "=" + value + "\n");
		}
		Writer writer = new StringWriter();
		PrintWriter printWriter = new PrintWriter(writer);
		ex.printStackTrace(printWriter);
		Throwable cause = ex.getCause();
		while (cause != null) {
			cause.printStackTrace(printWriter);
			cause = cause.getCause();
		}
		printWriter.close();
		// 得到错误信息
		String result = writer.toString();
		sb.append(result);
		// 存到文件
		long timestamp = System.currentTimeMillis();
		String time = formatter.format(new Date());
		String fileName = "crash-" + time + "-" + timestamp + ".log";
		if (Environment.getExternalStorageState().equals(
				Environment.MEDIA_MOUNTED)) {
			try {
				String path = Environment.getExternalStorageDirectory()
						.getCanonicalPath();
				FileOutputStream fos = new FileOutputStream(path + fileName);
				fos.write(sb.toString().getBytes());
				fos.close();
			} catch (IOException e) {
				// TODO Auto-generated catch block
				e.printStackTrace();
			}
		}
		return fileName;
	}

	/**
	 * 当uncaught发生时会转入该函数处理
	 */
	@Override
	public void uncaughtException(Thread thread, Throwable ex) {
		if (!handleException(ex) && mDefaultHandler != null) {
			// 如果用户没有处理则让系统默认的异常处理器来处理
			mDefaultHandler.uncaughtException(thread, ex);
		} else {
			try {
				Thread.sleep(3000);
			} catch (InterruptedException e) {
			}
			// 退出程序
			android.os.Process.killProcess(android.os.Process.myPid());
			System.exit(1);
		}
	}

	/** 获取CrashHandler实例 ,单例模式 */
	public static CrashHandler getInstance() {
		if (INSTANCE == null) {
			return INSTANCE = new CrashHandler();
		} else {
			return INSTANCE;
		}
	}
}

然后在application中调用它：

package com.xiaoqi.crashhandlerdemo;

import android.app.Application;

public class MyApplication extends Application {
	@Override
	public void onCreate() {
		CrashHandler crashHandler = CrashHandler.getInstance();
		crashHandler.init(getApplicationContext());
		super.onCreate();
	}
}

我们故意写一个空指针异常来试验一下：

public class MainActivity extends Activity {
	String s;

	@Override
	protected void onCreate(Bundle savedInstanceState) {
		super.onCreate(savedInstanceState);
		setContentView(R.layout.activity_main);
		System.out.println(s.equals("123"));

	}
}

结果:程序会提示有错，却不会直接崩溃