我刚刚开始使用Android,我遇到了以下问题:
我在打开新Activity时尝试saveInstanceState,当Activity恢复为Visible状态时我需要恢复该状态。
这是我的onSaveInstanceState方法
@Override
public void onSaveInstanceState(Bundle outState) {
super.onSaveInstanceState(outState);
outState.putParcelableArrayList("movies", (ArrayList<Movie>) movies);
Log.v("onSaveInstanceState ", "SAVING STATE");
Log.v("Saving State", outState.toString());
}
这是我的onCreate方法,应该恢复以前保存的实例状态
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
if (savedInstanceState != null){
Log.v("onCreate ", "EXISTING STATE");
this.movies = savedInstanceState.getParcelableArrayList("movies");
}else{
Log.v("onCreate ", "EMPTY STATE");
}
setHasOptionsMenu(true);
}
如果您注意到,在onSaveInstanceState方法中,在保存实例后,我在保存的实例上执行toString(),它会显示包含我保存的值的完整实例。但是,当我恢复实例时,savedInstanceState变量将为null。
我正在使用一个自定义对象Array,其中每个对象都实现了Parcelable。
以下是课程:
public class Movie implements Parcelable {
private String title;
private String path;
private String overview;
private String releaseDate;
private double vote;
public Movie(String title, String overview, double vote, String releaseDate, String path) {
this.title = title;
this.overview = overview;
this.vote = vote;
this.releaseDate = releaseDate;
this.path = path;
}
public String getTitle() {
return title;
}
public String getPath() {
return path;
}
public String getOverview() {
return overview;
}
public String getReleaseDate() {
return releaseDate;
}
public double getVote() {
return vote;
}
protected Movie(Parcel source){
this.title = source.readString();
this.path = source.readString();
this.overview = source.readString();
this.releaseDate = source.readString();
this.vote = source.readDouble();
}
public static final Creator<Movie> CREATOR = new Creator<Movie>() {
@Override
public Movie createFromParcel(Parcel source) {
return new Movie(source);
}
@Override
public Movie[] newArray(int size) {
return new Movie[size];
}
};
@Override
public int describeContents() {
return 0;
}
@Override
public void writeToParcel(Parcel dest, int flags) {
dest.writeString(title);
dest.writeSerializable(path);
dest.writeString(overview);
dest.writeString(releaseDate);
dest.writeDouble(vote);
}
@Override
public String toString() {
return "Movie{" +
"title='" + title + '\'' +
", path='" + path + '\'' +
", overview='" + overview + '\'' +
", releaseDate='" + releaseDate + '\'' +
", vote=" + vote +
'}';
}
}
我觉得我以某种方式以错误的方式保存它。我按照教程了解了如何做到这一点。请让我知道我做错了什么。谢谢
答案 0 :(得分:1)
通过在清单文件中添加MainActivity来解决我的问题。
android:launchMode="singleTop"
创建了多个Activity实例,因此不会保存实例。