Android性能优化程序员

内存泄露的一些坑

2017-09-08  本文已影响49人  大大大大大先生

Activity内部类泄漏

Activity内部Handler

class MyHandler extends Handler {
        
        MyHandler() {
            
        }

        @Override
        public void handleMessage(Message msg) {
            // to do your job
        }
    }
MyHandler myHandler = new MyHandler();

如上，在Activity内部如果声明一个这样的Handler，那么myHandler就默认持有Activity引用，假设Activity退出了，但是可能这时候才有myHandler的任务post，那么Activity是无法被回收的，可以采用以下方式解决：

static class MyHandler extends Handler {
        WeakReference<Activity> mActivityReference;

        MyHandler(Activity activity) {
            mActivityReference = new WeakReference<Activity>(activity);
        }

        @Override
        public void handleMessage(Message msg) {
            final Activity activity = mActivityReference.get();
            if (activity != null) {
                if (msg.what == 1 && isJumpToHomePage) {
                    Intent intent = new Intent(activity, HomePageActivity.class);
//                    intent.putExtra("themeType", themeType);
//                    LogUtil.d("themeType == " + themeType);
                    activity.startActivity(intent);
                    activity.finish();
                }
            }
        }
    }

这里面是把MyHandler是一个内部静态类，静态类在java虚拟机加载的时候就是独立加载到内存中的，不会依赖于任何其他类，而且这里面是把activity以弱引用的方式传到MyHandler中，即便是静态MyHandler类对象一直存在，但是由于它持有的是activity弱引用，在gc回收的时候activity对象是可以被回收的，另外注意一点，对于Handler的使用如果有sendEmptyMessageDelayed()来延迟任务执行的话最好在Activity的onDestroy里面把Handler的任务都移除（removeCallbacks(null)），activity在退出后，就是应该在onDestroy方法里面把一些任务取消掉，做一些清理的操作

Activity内部线程

Activity内部类回调监听

private static class RecorderTimeListener implements TimeCallback {

        WeakReference<ChatActivity> target;

        RecorderTimeListener(ChatActivity activity) {
            target = new WeakReference<>(activity);
        }

        @Override
        public void onCountDown(final int time) {
            if (target == null || target.get() == null) {
                return;
            }
            final ChatActivity activity = target.get();
            activity.runOnUiThread(new Runnable() {

                @Override
                public void run() {
                    activity.volumeView.setResetTime(time);
                }
            });
        }

        @Override
        public void onMaxTime() {
            if (target == null || target.get() == null) {
                return;
            }
            final ChatActivity activity = target.get();
            activity.runOnUiThread(new Runnable() {
                @Override
                public void run() {
                    activity.isMaxTime = true;
                    activity.stopRecord();
                }
            });
        }
    }

private class StartRecorderListener implements StartCallback {


        @Override
        public boolean onWait() {
            cancelRecord();
            return true;
        }

        @Override
        public void onStarted() {
            if (playerManager.isPlaying()) {
                playerManager.stop();
            }
            recordWaveView.setVisibility(View.VISIBLE);
            animation = (AnimationDrawable) recordWaveView.getBackground();
            animation.start();

            volumeView.showMoveCancelView();
            volumeDialog.show();

            viewHandler.postDelayed(volumeRunnable, 100);
        }

        @Override
        public void onFailed(int errorCode) {
            if (errorCode == RecorderManager.ERROR_START_FAIL) {
                showHintDialog(R.string.chat_permission_dialog_title, R.string.chat_permission_dialog_message);
            }
        }
    }

private void startRecord() {
        SystemDateUtil.init(this);
        LogUtil.i(ChatKey.TAG_INFO, "--------------------------录音开始--------------------------");
        final long startSendTime = SystemDateUtil.getCurrentDate().getTime();
        sliceSender = dialogMsgService.createSliceSender(
                AccountUtil.getCurrentFamilyChatDialogId(),
                AccountUtil.getCurrentImAccountId(), new DialogMsgService.OnSendVoiceMsgListener() {
                    @Override
                    public void onSuccess() {
                        LogUtil.d(TAG, "录音上传成功");
                        sendBigData(sliceSender.getGroupId(), ChatMsgBeh.MsgType.EMOJI,
                                SystemDateUtil.getCurrentDate().getTime() - startSendTime, SendMsgEvent.CODE_SEND_SUCCESS);
                    }

                    @Override
                    public void onFailure() {
                        sendBigData(sliceSender.getGroupId(), ChatMsgBeh.MsgType.EMOJI,
                                SystemDateUtil.getCurrentDate().getTime() - startSendTime, SendMsgEvent.CODE_SEND_FAILURE);
                        LogUtil.d(TAG, "录音上传失败");
                    }
                });
        RecorderManager.getInstance(this).startRecorder(sliceSender, new StartRecorderListener(), new RecorderTimeListener(this));
        LogUtil.i(ChatKey.TAG_INFO, "groupId:" + sliceSender.getGroupId());
    }

如上StartRecorderListener是内部类，RecorderTimeListener是静态内部类并传入Activity弱引用，如果把StartRecorderListener的实现改成RecorderTimeListener的实现，那么Activity内存泄漏就不存在了

动画导致内存泄漏

自定义控件ImageButton中：
public void start(float startAngle, float endAngle) {
        setStop(false);

        final AnimatorSet as = new AnimatorSet();
        final ObjectAnimator oa = ObjectAnimator.ofFloat(this, "progress",
                startAngle, endAngle);
        oa.setDuration(duration);
        oa.setInterpolator(new DecelerateInterpolator(1.1f));
        oa.setRepeatCount(count);
//      oa.setRepeatMode(ObjectAnimator.INFINITE);
        oa.addUpdateListener(new AnimatorUpdateListener() {

            @Override
            public void onAnimationUpdate(ValueAnimator animator) {
                if (stop && as.isRunning()) {
                    as.cancel();
//                    oa.removeAllListeners();
                } else {
                    float p = (float) animator.getAnimatedValue();
                    setProgress(p);
                }
            }
        });
        as.addListener(new AnimatorListenerAdapter() {
            @Override
            public void onAnimationEnd(Animator animation) {
            }
        });
        as.play(oa);
        as.start();
    }
    
    public void cancel() {
        setStop(true);
    }

    public void setStop(boolean stop) {
        this.stop = stop;
        if (stop) {
            setProgress(0.0f);
        }
    }

如上如果不cancel掉属性动画就会一直运行并且一直去执行控件的onDraw方法，那么ImageButton持有了Activity对象，而属性动画ObjectAnimator持有了ImageButton，ObjectAnimator一直在运行，那么Activity对象也就不能被释放了

private static ValueAnimator valueAnimator;

private void startValueAnimator() {
        int displayTime2Show = displayTime - 1;
        if (displayTime2Show > 1) {
            valueAnimator = ValueAnimator.ofInt(displayTime2Show, 1);
            valueAnimator.setDuration(displayTime2Show * 1000);
            valueAnimator.addUpdateListener(new ValueAnimator.AnimatorUpdateListener() {
                @Override
                public void onAnimationUpdate(ValueAnimator animation) {
                    tvStartPageTime.setText(animation.getAnimatedValue().toString());
                }
            });
            valueAnimator.start();
        }

    }

protected void onPause() {
        if (valueAnimator != null && valueAnimator.isRunning()) {
            valueAnimator.cancel();
            valueAnimator = null;
        }
        super.onPause();
    }

即便是在activity退出后cancel掉动画，activity依然无法被释放，为什么？因为valueAnimator是静态的，而且添加了动画属性改变的监听addUpdateListener，在监听回调里面有tvStartPageTime（TextView）控件，默认持有Activity对象，因此即便Activity退出，动画cancel掉也无法释放持有的引用，修改方法有两种，一种是把valueAnimator的static修饰去掉，另一中国是：

protected void onPause() {
valueAnimator.removeAllUpdateListeners();
        if (valueAnimator != null && valueAnimator.isRunning()) {
            valueAnimator.cancel();
            valueAnimator = null;
        }
        super.onPause();
    }

加一句监听器的移除代码removeAllUpdateListeners()

传Context参数的时候使用Activity对象造成内存泄漏

在Android5.0以上的WebView泄漏

子线程中不当的使用Looper.prepare()和Looper.loop()方法造成内存泄漏

EditText使用setTransformationMethod导致的内存泄漏

loginPasswdEt.setTransformationMethod(PasswordTransformationMethod.getInstance());
loginPasswdEt.setTransformationMethod(HideReturnsTransformationMethod.getInstance());

而PasswordTransformationMethod和HideReturnsTransformationMethod分别都是一个单例：

private static PasswordTransformationMethod sInstance;

private static HideReturnsTransformationMethod sInstance;

PasswordTransformationMethod

public CharSequence getTransformation(CharSequence source, View view) {
        if (source instanceof Spannable) {
            Spannable sp = (Spannable) source;

            /*
             * Remove any references to other views that may still be
             * attached.  This will happen when you flip the screen
             * while a password field is showing; there will still
             * be references to the old EditText in the text.
             */
            ViewReference[] vr = sp.getSpans(0, sp.length(),
                                             ViewReference.class);
            for (int i = 0; i < vr.length; i++) {
                sp.removeSpan(vr[i]);
            }

            removeVisibleSpans(sp);

            sp.setSpan(new ViewReference(view), 0, 0,
                       Spannable.SPAN_POINT_POINT);
        }

        return new PasswordCharSequence(source);
    }
    
private static class ViewReference extends WeakReference<View>
            implements NoCopySpan {
        public ViewReference(View v) {
            super(v);
        }
    }

上面是5.0系统的源码，里面已经用ViewReference来包装view设置到Spannable中了，所以是把view的弱引用传进去了，因此可以被gc回收，而在4.0android系统上，很可能就不是这么做的，所以4.0系统上面就是View对象被PasswordTransformationMethod和HideReturnsTransformationMethod单例长期持有，而View又持有Activity对象，所以针对4.0系统我们只需要释放这两个单例对象即可：

private void releaseMemoryLeak() {
        int sdk = Build.VERSION.SDK_INT;
        if (sdk >= Build.VERSION_CODES.LOLLIPOP) {
            return;
        }
        try {
            Field field1 = PasswordTransformationMethod.class.getDeclaredField("sInstance");
            if (field1 != null) {
                field1.setAccessible(true);
                field1.set(PasswordTransformationMethod.class, null);
            }
            Field field2 = HideReturnsTransformationMethod.class.getDeclaredField("sInstance");
            if (field2 != null) {
                field2.setAccessible(true);
                field2.set(HideReturnsTransformationMethod.class, null);
            }
        } catch (NoSuchFieldException e) {
            SyncLogUtil.e(e);
        } catch (IllegalAccessException e) {
            SyncLogUtil.e(e);
        }
    }

加上上述代码后验证发现内存不再泄漏，搞定。

控件的BackGround导致的内存泄漏（4.0android系统已经解决）

private static Drawable sBackground;
@Override
protected void onCreate(Bundle state) {
  super.onCreate(state);

  TextView label = new TextView(this);
  label.setText("Leaks are bad");

  if (sBackground == null) {
    sBackground = getDrawable(R.drawable.large_bitmap);
  }
  label.setBackgroundDrawable(sBackground);

  setContentView(label);
}

因为在View的setBackgroundDrawable方法里面有一句：

public void setBackgroundDrawable(Drawable background) {
......省略很多代码
background.setCallback(this);
mBackground = background;
}

Drawable对象把View对象作为回调保存起来了，不过在4.0系统以后引入回调来保存View对象了，所以已经不会造成内存泄漏问题了：

public final void setCallback(Callback cb) {
        mCallback = new WeakReference<Callback>(cb);
    }

这里依然要举例子出来是想说明不恰当的使用static来修饰变量很有可能导致对象无法被回收

上一篇 下一篇

猜你喜欢

热点阅读