Android内存泄露自动检测LeakCanary

经典的面试题：

a、怎样在coding过程中避免内存泄露？

b、怎样检测内存泄露？

这两个问题我想大部分Android 职位面试时都会被问到吧。

    怎样避免就不赘述了，网上很多答案。   工具呢，当然也有很多，比如DDMS、MAT等，但是怎样在我们编码过程中植入内存检测代码，让我们程序在开发调试阶段就能发现内存泄露呢？好了，现在该大名鼎鼎的LeakCanary出场了，它是Square公司的一个内存探测开源项目。下面就介绍下怎样使用.

1、配置gradle依赖:

    debugCompile 'com.squareup.leakcanary:leakcanary-android:1.3.1'    releaseCompile 'com.squareup.leakcanary:leakcanary-android-no-op:1.3.1'
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2、初始化Watcher

package com.micky.leakcanarysamples;;import android.app.Application;import com.squareup.leakcanary.LeakCanary;import com.squareup.leakcanary.RefWatcher;/** * @Project LeakCanaryTest * @Packate com.micky.leakcanarysamples; * @Description * @Author Micky Liu * @Email [e-mail] * @Date 2016-01-04 10:32 * @Version 1.0 */public class BaseApplication extends Application {    private static BaseApplication instance;    private RefWatcher mRefWatcher;    @Override    public void onCreate() {        super.onCreate();        instance = this;        mRefWatcher = Constants.DEBUG ?  LeakCanary.install(this) : RefWatcher.DISABLED;    }    public static BaseApplication getInstance() {        return instance;    }    public static RefWatcher getRefWatcher() {        return getInstance().mRefWatcher;    }}
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3、在Activity或Fragment中添加检测

package com.micky.leakcanarysamples;import android.app.Activity;import android.support.v7.app.AppCompatActivity;/** * @Project LeakCanaryTest * @Packate com.micky.leakcanarysamples; * @Description * @Author Micky Liu * @Email [e-mail] * @Date 2016-01-04 10:39 * @Version 1.0 */public class BaseActivity extends AppCompatActivity {    @Override    protected void onDestroy() {        super.onDestroy();        BaseApplication.getRefWatcher().watch(this);    }}
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4、测试

package com.micky.leakcanarysamples;;import android.os.Bundle;import android.os.Handler;/** * @Project LeakCanaryTest * @Packate com.micky.leakcanarysamples; * @Description * @Author Micky Liu * @Email [e-mail] * @Date 2016-01-04 10:29 * @Version 1.0 */public class TestActivity extends BaseActivity {    private final Handler mHandler = new Handler();    @Override    protected void onCreate(Bundle savedInstanceState) {        super.onCreate(savedInstanceState);        //模拟内存泄露        mHandler.postDelayed(new Runnable() {            @Override            public void run() {            }        }, 3 * 60 * 1000);        finish();    }}
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5、测试结果

a、Toast显示（大概10秒左右显示）

b、通知显示

c、桌面自动添加的图标

d、内存泄露列表 

e、内存泄露详细 

LogCat可以看到日志日下（hprof文件可以用MAT打开进行分析）：

01-04 11:49:41.815 12967-13004/com.micky.leakcanarysamples I/dalvikvm: hprof: dumping heap strings to "/storage/emulated/0/Download/leakcanary/suspected_leak_heapdump.hprof".01-04 11:49:42.020 12967-13004/com.micky.leakcanarysamples I/dalvikvm: hprof: heap dump completed (28850KB)
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查看自动生成的AndroidManifest文件，LeakCanarySamples/app/build/intermediates/manifests/full/debug/AndroidManifest.xml

<?xml version="1.0" encoding="utf-8"?><manifest xmlns:android="http://schemas.android.com/apk/res/android"    package="com.micky.leakcanarysamples"    android:versionCode="1"    android:versionName="1.0" >    <uses-sdk        android:minSdkVersion="10"        android:targetSdkVersion="23" />    <!-- To store the heap dumps and leak analysis results. -->    <uses-permission android:name="android.permission.WRITE_EXTERNAL_STORAGE" />    <android:uses-permission android:name="android.permission.READ_EXTERNAL_STORAGE" />    <application        android:name="com.micky.leakcanarysamples.BaseApplication"        android:allowBackup="true"        android:icon="@mipmap/ic_launcher"        android:label="@string/app_name"        android:supportsRtl="true"        android:theme="@style/AppTheme" >        <activity            android:name="com.micky.leakcanarysamples.MainActivity"            android:label="@string/app_name"            android:theme="@style/AppTheme.NoActionBar" >            <intent-filter>                <action android:name="android.intent.action.MAIN" />                <category android:name="android.intent.category.LAUNCHER" />            </intent-filter>        </activity>        <activity android:name="com.micky.leakcanarysamples.TestActivity" />        <service            android:name="com.squareup.leakcanary.internal.HeapAnalyzerService"            android:enabled="false"            android:process=":leakcanary" />        <service            android:name="com.squareup.leakcanary.DisplayLeakService"            android:enabled="false" />        <activity            android:name="com.squareup.leakcanary.internal.DisplayLeakActivity"            android:enabled="false"            android:icon="@drawable/__leak_canary_icon"            android:label="@string/__leak_canary_display_activity_label"            android:taskAffinity="com.squareup.leakcanary"            android:theme="@style/__LeakCanary.Base" >            <intent-filter>                <action android:name="android.intent.action.MAIN" />                <category android:name="android.intent.category.LAUNCHER" />            </intent-filter>        </activity>    </application></manifest>
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如上所示LeakCanary给我们自动添加了两个Service和一个Activity，并添加了对SD卡的读写权限

It ‘s so simple. 
注:

1、如果在Release模式下请使用RefWatcher.DISABLED

2、在Activity或Fragment 的 Destroy方法中添加检测（很好理解，就是判断一个Activity或Fragment想要被销毁的时候，是否还有其他对象持有其引用导致Activity或Fragment不能被回收，从而导致内存泄露)

源码地址:https://github.com/mickyliu945/LeakCanarySample