Activity嵌套Fragment应用放置后台很久，被系统回收，出现crash
由于使用了主界面的 东西比较多 占用内存比较大，在程序进入后台后，长时间不操作被系统回收 ，再次 进入程序后导致程序崩溃。错误日志：
Parcel android.os.Parcel@42209460: Unmarshalling unknown type code
2131165303 at offset 3748
at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2080)
at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2105)
at android.app.ActivityThread.access$600(ActivityThread.java:136)
at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1201)
at android.os.Handler.dispatchMessage(Handler.java:99)
at android.os.Looper.loop(Looper.java:137)
at android.app.ActivityThread.main(ActivityThread.java:4876)
at java.lang.reflect.Method.invokeNative(Native Method)
at java.lang.reflect.Method.invoke(Method.java:511)
at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:804)
at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:571)
at com.kdgdev.xtension.core.XtensionMain.main(XtensionMain.java:91)
at dalvik.system.NativeStart.main(Native Method)
定位至报错位置
FragmentActivity的super.onCreate(savedInstanceState);恢复现场时报错
我们查看报错的FragmentActivity的源码：
FragmentActivity
protected void onSaveInstanceState(Bundle outState)
{
super.onSaveInstanceState(outState);
Parcelable p = this.mFragments.saveAllState();
if (p != null)
outState.putParcelable("android:support:fragments", p);
}static final String FRAGMENTS_TAG = "android:support:fragments";
/**
* Perform initialization of all fragments and loaders.
*/
@Override
protected void onCreate(Bundle savedInstanceState) {
mFragments.attachActivity(this, mContainer, null);
// Old versions of the platform didn't do this!
if (getLayoutInflater().getFactory() == null) {
getLayoutInflater().setFactory(this);
}
super.onCreate(savedInstanceState);
NonConfigurationInstances nc = (NonConfigurationInstances)
getLastNonConfigurationInstance();
if (nc != null) {
mAllLoaderManagers = nc.loaders;
}
if (savedInstanceState != null) {
Parcelable p = savedInstanceState.getParcelable(FRAGMENTS_TAG);
mFragments.restoreAllState(p, nc != null ? nc.fragments : null);
}
mFragments.dispatchCreate();
}崩溃时做了保存View状态的处理，崩溃恢复后解包getParcelable(FRAGMENTS_TAG) 恢复View状态发生移位错误（某种异常情况下，如对象不是Parcelable、 writeToParcel和createFromParcel无对应等 ）
多方定位发现是AutoScrollTextView 的实现由问题，导致崩溃时View状态保存有误：
查看报错位置：
查看报错位置：
public class AutoScrollTextView extends TextView implements OnClickListener {
public final static String TAG = AutoScrollTextView.class.getSimpleName();
private float textLength = 0f;//文本长度
private float viewWidth = 0f;
private float step = 0f;//文字的横坐标
private float y = 0f;//文字的纵坐标
private float temp_view_plus_text_length = 0.0f;//用于计算的临时变量
private float temp_view_plus_two_text_length = 0.0f;//用于计算的临时变量
public boolean isStarting = false;//是否开始滚动
private Paint paint = null;//绘图样式
private String text = "";//文本内容
public AutoScrollTextView(Context context) {
super(context);
initView();
}
public AutoScrollTextView(Context context, AttributeSet attrs) {
super(context, attrs);
initView();
}
public AutoScrollTextView(Context context, AttributeSet attrs, int defStyle) {
super(context, attrs, defStyle);
initView();
}
private void initView()
{
setOnClickListener(this);
}
public void init(WindowManager windowManager)
{
paint = getPaint();
text = getText().toString();
textLength = paint.measureText(text);
viewWidth = getWidth();
if(viewWidth == 0)
{
if(windowManager != null)
{
Display display = windowManager.getDefaultDisplay();
viewWidth = display.getWidth();
}
}
step = textLength;
temp_view_plus_text_length = viewWidth + textLength;
temp_view_plus_two_text_length = viewWidth + textLength * 2;
y = getTextSize() + getPaddingTop();
}
@Override
public Parcelable onSaveInstanceState()
{
Parcelable superState = super.onSaveInstanceState();
SavedState ss = new SavedState(superState);
ss.step = step;
ss.isStarting = isStarting;
return ss;
}
@Override
public void onRestoreInstanceState(Parcelable state)
{
if (!(state instanceof SavedState)) {
super.onRestoreInstanceState(state);
return;
}
SavedState ss = (SavedState)state;
super.onRestoreInstanceState(ss.getSuperState());
step = ss.step;
isStarting = ss.isStarting;
}
public static class SavedState extends BaseSavedState {
public boolean isStarting = false;
public float step = 0.0f;
SavedState(Parcelable superState) {
super(superState);
}
@Override
public void writeToParcel(Parcel out, int flags) {
super.writeToParcel(out, flags);
out.writeBooleanArray(new boolean[]{isStarting});
out.writeFloat(step);
}
public static final Parcelable.Creator CREATOR
= new Parcelable.Creator() {
public SavedState[] newArray(int size) {
return new SavedState[size];
}
@Override
public SavedState createFromParcel(Parcel in) {
return new SavedState(in);
}
};
private SavedState(Parcel in) {
super(in);
boolean[] b = null;
in.readBooleanArray(b);
if(b != null && b.length > 0)
isStarting = b[0];
step = in.readFloat();
}
}
public void startScroll()
{
isStarting = true;
invalidate();
}
public void stopScroll()
{
isStarting = false;
invalidate();
}
@Override
public void onDraw(Canvas canvas) {
canvas.drawText(text, temp_view_plus_text_length - step, y, paint);
if(!isStarting)
{
return;
}
step += 0.5;//0.5为文字滚动速度。
if(step > temp_view_plus_two_text_length)
step = textLength;
invalidate();
}
@Override
public void onClick(View v) {
if(isStarting)
stopScroll();
else
startScroll();
}
} 跑马灯中重写TextView中自定义实现SavedState导致的解包异常，注释掉SavedState的实现即恢复正常。大部分应用都是这样，销毁了进来重新create了，所以你要把报错的地方判断一下就好了，因此另一种解决办法就是在FragmentActivity的onCreate做判断：
if (savedInstanceState != null) {
savedInstanceState.putParcelable("android:support:fragments", null);
}
super.onCreate(savedInstanceState);if (savedInstanceState != null) {
savedInstanceState.putParcelable("android:fragments", null);
}
super.onCreate(savedInstanceState);