在使用add加载Fragment,并且使用show,hide来控制Fragment,如果没有相关恢复处理,在页面被强杀重启后,就会导致这多个Fragment都是show的形态显示,即多个布局叠加在Activity上
原理:
app进入后台、屏幕旋转前、跳转下一个Activity,内存不足被强杀,app崩溃等时候,fragment走了onSaveInstance方法,它保存了`final class FragmentState implements Parcelable {
final String mClassName;
final int mIndex;
final boolean mFromLayout;
final int mFragmentId;
final int mContainerId;
final String mTag;
final boolean mRetainInstance;
final boolean mDetached;
final Bundle mArguments;
…
但是它并没有保存fragment等mHidden状态,所以才会造成重叠
解决方法:
public class BaseFragment extends Fragment {
private static final String STATE_SAVE_IS_HIDDEN = "STATE_SAVE_IS_HIDDEN";
@Override
public void onCreate(@Nullable Bundle savedInstanceState) {
...
if (savedInstanceState != null) {
boolean isSupportHidden = savedInstanceState.getBoolean(STATE_SAVE_IS_HIDDEN);
FragmentTransaction ft = getFragmentManager().beginTransaction();
if (isSupportHidden) {
ft.hide(this);
} else {
ft.show(this);
}
ft.commit();
}
@Override
public void onSaveInstanceState(Bundle outState) {
...
outState.putBoolean(STATE_SAVE_IS_HIDDEN, isHidden());
}
}
在onCreate等初始化生命周期内加载Fragment,为了防重复加载Fragment,在页面重启时就不要再去加载Fragment了
public class MainActivity ... {
@Override
protected void onCreate(@Nullable Bundle savedInstanceState) {
...
// 这里一定要在save为null时才加载Fragment,Fragment中onCreateView等生命周里加载根子Fragment同理
// 因为在页面重启时,Fragment会被保存恢复,而此时再加载Fragment会重复加载,导致重叠
if(saveInstanceState == null){
// 正常情况下去 加载根Fragment
}
}
}