如何以编程方式保存屏幕截图而不会覆盖之前拍摄的屏幕截图？

Question

I'm working on an android application and I want to save a screenshot of the application. I can save a single screenshot but it keeps over writing the previous screenshot. I followed a tutorial and modified it but it does not take more than a single screenshot

Attached here is the code in the button action

      case R.id.btn_save:
            View rootView = getWindow().getDecorView().findViewById(android.R.id.content);
            Bitmap bitmap = getScreenShot(rootView);
            int i = 0;
            File file = new File("ScreenShot"+ i +".PNG");
            if(!file.exists()){
                store(bitmap, "ScreenShot"+ i +".PNG");
            }
            else {
                store(bitmap, "ScreenShot"+ i++ +".PNG");
            }

and the screenshot storing function

public void store(Bitmap bm, String fileName){
    String dirPath = Environment.getExternalStorageDirectory().getAbsolutePath() + "/Screenshots";
    File dir = new File(dirPath);
    if (!dir.exists()){
        dir.mkdirs();
    }
    File file = new File(dirPath,fileName);
    try{
        FileOutputStream fos = new FileOutputStream(file);
        bm.compress(Bitmap.CompressFormat.PNG, 100,fos);
        fos.flush();
        fos.close();
    }catch (Exception e){
        e.printStackTrace();
        Toast.makeText(this, "Error saving File", Toast.LENGTH_SHORT).show();
    }
}

Answer 1

You are declaring i variable inside the button save so you will always start with 0 when button is clicked. To use the way you are trying you should declare that variable outside that scope, but it will restart when you kill and reopen the app.

You can use Shared Preferences to save the following number to use (or the last you used) if you want to use that approach. If not you can use simply

"Screenshot" + System.currentTimeInMillis().toString(). 

You will also have the time when the screenshot was taken (although in millis). If you want you can format it to be like "user readable" 20191110 for example

Answer 2

Because in that code the file name is always the same- i is always 0. To make it work for one use of the app, i should be a member variable and incremented every screenshot. To make it work more generally, you should generate a random name using File.createTempFile()

Answer 3

case R.id.btn_save:
   View rootView getWindow().getDecorView().findViewById(android.R.id.content);
   Bitmap bitmap = getScreenShot(rootView);

   File dir = new File(Environment.getExternalStorageDirectory(), "Screenshots");

   if (!dir.exists())
    if ( !dir.mkdirs())
        {
          Toast ( could not create dir...);
          return;
        }

 int i = 0;
 while (++i > 0 )
  {
  String fileName = "ScreenShot"+ i +".png";

  File file = new File(dir, fileName);
  if(!file.exists())
       {
         store(bitmap, file);

         break;
        }
  }
  break;     

Change the parameter of store(Bitmap bm, String fileName) to store(Bitmap bm, File file)

There you can remove all code before the try block.