我在文件管理器应用程序中有一个主要 Activity 和一个适配器。因此，当我在应用程序中打开一个文件夹，然后打开一个子文件夹，然后按后退按钮时，它会返回到主屏幕/主屏幕。
我想按“返回”返回子文件夹屏幕，然后按“返回”返回文件夹屏幕，然后按“返回”返回主屏幕。
但是现在，当我按后退按钮时，我会直接返回主屏幕。
我怎样才能实现这个目标？
InternalStorage.java:
public class InternalStorage extends AppCompatActivity implements MyRecyclerViewAdapter.ItemClickListener {
MyRecyclerViewAdapter adapter;
private ArrayList<String> myList, myList2,;
String path = Environment.getExternalStorageDirectory().getAbsolutePath();
public static boolean selectallflag = false;
RecyclerView recyclerView;
private static final String TAG = "com.example.dell_1.myapp3.InternalMemory";
File f = new File(path);//converted string object to file//getting the list of files in string array
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_internal_storage);
method1(f);
method2(f);
// set up the RecyclerView
setAdapter();
}
@Override
public void onItemClick(View view, int position) {
String string1 = adapter.getItem(position);
final File directory = new File(string1);
if (directory.isDirectory()) {
method1(directory);
method2(directory);
setAdapter():
} else if (string1.endsWith(".mp3")) {
Intent viewIntent1 = new Intent(Intent.ACTION_VIEW);
viewIntent1.setDataAndType(Uri.fromFile(directory), "audio/mpeg");
startActivity(Intent.createChooser(viewIntent1, null));
} else if (string1.endsWith(".zip")) {
Intent viewIntent1 = new Intent(Intent.ACTION_VIEW);
viewIntent1.setDataAndType(Uri.fromFile(directory), "application/zip");
startActivity(Intent.createChooser(viewIntent1, null));
} else if (string1.endsWith(".mp4")) {
Intent viewIntent1 = new Intent(Intent.ACTION_VIEW);
viewIntent1.setDataAndType(Uri.fromFile(directory), "video/mp4");
startActivity(Intent.createChooser(viewIntent1, null));
} else if (string1.endsWith(".jpeg")) {
Intent viewIntent1 = new Intent(Intent.ACTION_VIEW);
viewIntent1.setDataAndType(Uri.fromFile(directory), "image/*");
startActivity(Intent.createChooser(viewIntent1, null));
} else if (string1.endsWith(".png")) {
Intent viewIntent1 = new Intent(Intent.ACTION_VIEW);
viewIntent1.setDataAndType(Uri.fromFile(directory), "image/*");
startActivity(Intent.createChooser(viewIntent1, null));
} else if (string1.endsWith(".pdf")) {
Intent viewIntent1 = new Intent(Intent.ACTION_VIEW);
viewIntent1.setDataAndType(Uri.fromFile(directory), "application/pdf");
startActivity(Intent.createChooser(viewIntent1, null));
} else if (string1.endsWith(".apk")) {
Intent viewIntent1 = new Intent(Intent.ACTION_VIEW);
viewIntent1.setDataAndType(Uri.fromFile(directory), "application/vnd.android.package-archive");
startActivity(Intent.createChooser(viewIntent1, null));
} else if (string1.endsWith(".txt")) {
Intent viewIntent1 = new Intent(Intent.ACTION_VIEW);
viewIntent1.setDataAndType(Uri.fromFile(directory), "text/*");
startActivity(Intent.createChooser(viewIntent1, null));
} else Toast.makeText(this, "unsupported format", Toast.LENGTH_SHORT)
.show();
}
public ArrayList<String> method1(File f) {
File list2[] = f.listFiles();
myList = new ArrayList<>();
if (list2 != null) {
for (int i = 0; i < list2.length; i++) {
myList.add(list2[i].getName());
}
} else Toast.makeText(this, "the folder is empty", Toast.LENGTH_SHORT)
.show();
return myList;
}
public ArrayList<String> method2(File f) {
File list2[] = f.listFiles();
myList2 = new ArrayList<>();
if (list2 != null) {
for (int i = 0; i < list2.length; i++) {
myList2.add(list2[i].getPath());
}
} else Toast.makeText(this, "the folder is empty", Toast.LENGTH_SHORT)
.show();
return myList2;
}
@Override
public void onBackPressed() {
selectallflag =false;
super.onBackPressed();
}
private void setAdapter(){
RecyclerView recyclerView = (RecyclerView) findViewById(R.id.rvNumbers);
int numberOfColumns = 4;
recyclerView.setLayoutManager(new GridLayoutManager(this, numberOfColumns));
adapter = new MyRecyclerViewAdapter(this, myList, myList2);
adapter.setClickListener(this);
recyclerView.setAdapter(adapter);
}
}
MyRecyclerViewAdapter.java:
public class MyRecyclerViewAdapter extends RecyclerView.Adapter<MyRecyclerViewAdapter.ViewHolder> {
private ArrayList<String> mData;
private ArrayList<String> mData2;
private LayoutInflater mInflater;
private int selected_position ;
private ItemClickListener mClickListener;
private ArrayList<String> mSelected = new ArrayList<>();
ArrayList<Uri> files = new ArrayList<>();
private static final String TAG = "com.example.dell_1.myapp3.InternalMemory";
private Context context;
// data is passed into the constructor
public MyRecyclerViewAdapter(Context context, ArrayList<String> data, ArrayList<String> data2) {
this.mInflater = LayoutInflater.from(context);
this.mData = data;
this.mData2 = data2;
this.context = context;
}
// inflates the cell layout from xml when needed
@Override
public ViewHolder onCreateViewHolder(ViewGroup parent, int viewType) {
View view = mInflater.inflate(R.layout.recyclerview_item, parent, false);
return new ViewHolder(view);
}
// binds the data to the textview in each cell
@Override
public void onBindViewHolder(ViewHolder holder, int position) {
String animal = mData.get(position);
String animal2 = mData2.get(position);
int THUMBSIZE = 150;
Bitmap ThumbImage = ThumbnailUtils.extractThumbnail(BitmapFactory.decodeFile(animal2),
THUMBSIZE, THUMBSIZE);
Bitmap thumb = ThumbnailUtils.createVideoThumbnail(animal2, MediaStore.Video.Thumbnails.MINI_KIND);
holder.myTextView.setText(animal + "");
if(animal!= null && animal.endsWith(".mp3")){
holder.myImage.setImageResource(R.drawable.song);
}
else if(animal!= null && animal.endsWith(".pdf")){
holder.myImage.setImageResource(R.drawable.pdficon2);
}
else
if(animal!= null && animal.endsWith(".jpeg") && BitmapFactory.decodeFile(animal2)!=null ){
holder.myImage.setImageBitmap(ThumbImage);
}
else
if(animal!= null && animal.endsWith(".png") && BitmapFactory.decodeFile(animal2)!=null ){
holder.myImage.setImageBitmap(ThumbImage);
}
else
if(animal!= null && animal.endsWith(".mp4")){
holder.myImage.setImageBitmap(thumb);
}
else
if(animal!= null && animal.endsWith(".zip")){
holder.myImage.setImageResource(R.drawable.zip);
}
else
if(animal!= null && animal.endsWith(".aac")){
holder.myImage.setImageResource(R.drawable.song);
}
else
if(animal!= null && animal.endsWith(".txt")){
holder.myImage.setImageResource(R.drawable.text);
}
else if(animal!= null && animal.endsWith(".apk")){
PackageInfo packageInfo = context.getPackageManager()
.getPackageArchiveInfo(animal2, PackageManager.GET_ACTIVITIES);
if(packageInfo != null) {
ApplicationInfo appInfo = packageInfo.applicationInfo;
appInfo.sourceDir = animal2;
appInfo.publicSourceDir = animal2;
Drawable icon = appInfo.loadIcon(context.getPackageManager());
Bitmap bmpIcon = ((BitmapDrawable) icon).getBitmap();
holder.myImage.setImageBitmap(bmpIcon);
}
}
else {
holder.myImage.setImageResource(R.drawable.folder);
}
if(selectallflag){
holder.itemView.setBackgroundColor(Color.MAGENTA);
}
}
// total number of cells
@Override
public int getItemCount() {
return mData2.size();
}
// stores and recycles views as they are scrolled off screen
public class ViewHolder extends RecyclerView.ViewHolder implements View.OnClickListener, View.OnLongClickListener {
TextView myTextView;
ImageButton myImage;
ViewHolder(View itemView) {
super(itemView);
myImage = (ImageButton) itemView.findViewById(R.id.buttonimage);
myTextView = (TextView) itemView.findViewById(R.id.info_text);
myImage.setOnClickListener(this);
myImage.setOnLongClickListener(this);
}
@Override
public void onClick(View view) {
if (mClickListener != null) mClickListener.onItemClick(view, getAdapterPosition());
}
// convenience method for getting data at click position
public String getItem(int id) {
return mData2.get(id);
}
// allows clicks events to be caught
public void setClickListener(ItemClickListener itemClickListener) {
this.mClickListener = itemClickListener;
}
// parent activity will implement this method to respond to click events
public interface ItemClickListener {
void onItemClick(View view, int position);
boolean onLongClick(View view,int position);
}
最佳答案
您可以尝试创建一个堆栈条目来实现您的要求，请按照以下步骤操作
1.创建列表/堆栈
Stack<String> stack = new Stack<String>();
2.每当移动到子目录时添加一个条目
stack.push("nameofthescreen");
3.在 onBackPress() 方法上 检查堆栈中的条目
if(stack.size()>0)
{
String screenName=stack.pop();
//replace the screens you want as per the string you gave
}
else{
//No entries in the stack you can move to main screen by
super.onBackPress();
//or write custom code as you required
}
关于java - 避免按后退按钮退出应用程序，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/48779652/