Question

我的应用程序有一个下载功能花一些时间下载图像，我试图在图像下载时添加ProgressDialog。 ProgressDialog永远不会出现请帮帮我

这是我保存图片的代码：

private String saveImage(Bitmap image) {
    ProgressDialog pd = new ProgressDialog(Pop.this);
    pd.setMessage("Downloading ...");
    pd.show();
    String savedImagePath = null;
    String imageFileName = "vapor"+System.currentTimeMillis()+ ".png";
    File storageDir = new File(
            Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_PICTURES)
                    + "/vaporwave");
    boolean success = true;
    if (!storageDir.exists()) {
        success = storageDir.mkdirs();
    }
    if (success) {
        File imageFile = new File(storageDir, imageFileName);
        savedImagePath = imageFile.getAbsolutePath();
        try {
            OutputStream fOut = new FileOutputStream(imageFile);
            image.compress(Bitmap.CompressFormat.PNG, 100, fOut);
            fOut.close();
        } catch (Exception e) {
            e.printStackTrace();
        }
        // Add the image to the system gallery
        galleryAddPic(savedImagePath);
        Toast.makeText(Pop.this, "IMAGE SAVED", Toast.LENGTH_LONG).show();
        pd.dismiss();
    }
    return savedImagePath;
}

Answer 1

你应该使用像AsyncTask那样的后台任务，你不应该在你的UI线程上做复杂的任务。（否则你的UI会运气直到完成任务，所以你的progressDialog永远不会显示）

您可以阅读有关AsyncTask Here

的信息

例如在async中：

1）在onPreExecute

上显示您的progressDialog

2）并在onPostExecute

中将其解雇

3）并在doInBackground中完成工作（保存图片）（此方法中的返回类型将传递给onPostExecute）

public class saveImage extends AsyncTask<Bitmap,Void,String>{
    ProgressDialog pd;
    @Override
    protected void onPreExecute() {
        super.onPreExecute();
        pd = new ProgressDialog(Pop.this);
        pd.setMessage("Downloading ...");
        pd.show();
    }

    @Override
    protected String doInBackground(Bitmap... params) {
        Bitmap image = params[0];
        String savedImagePath = null;
        String imageFileName = "vapor"+System.currentTimeMillis()+ ".png";
        File storageDir = new File(
                Environment.getExternalStoragePublicDirectory(Environment.DIRECTORY_PICTURES)
                        + "/vaporwave");
        boolean success = true;
        if (!storageDir.exists()) {
            success = storageDir.mkdirs();
        }
        if (success) {
            File imageFile = new File(storageDir, imageFileName);
            savedImagePath = imageFile.getAbsolutePath();
            try {
                OutputStream fOut = new FileOutputStream(imageFile);
                image.compress(Bitmap.CompressFormat.PNG, 100, fOut);
                fOut.close();
            } catch (Exception e) {
                e.printStackTrace();
            }
            // Add the image to the system gallery
            galleryAddPic(savedImagePath);
            Toast.makeText(Pop.this, "IMAGE SAVED", Toast.LENGTH_LONG).show();
            pd.dismiss();
        }
        return savedImagePath;
    }

    @Override
    protected void onPostExecute(String s) {
        super.onPostExecute(s);
        //s is your savedImagePath
        pd.dismiss();
    }
}

你可以像这样调用这个任务：

    new saveImage().execute(yourBitmap);

图像下载时显示ProgressDialog

1 个答案: