放置ProgressDialog.dismiss方法时无法显示ProgressDialog

Question

当我在代码上添加progressDialog.dismiss()方法时， ProgressDialog无法显示

我还尝试添加Thread.sleep()以便它的执行会休眠一段时间，这可能会显示progressdialog一段时间，但这也行不通。

import android.app.ProgressDialog;
import android.content.Context;
import android.content.pm.ResolveInfo;
import android.os.Environment;
import android.widget.Toast;

import java.io.BufferedInputStream;
import java.io.BufferedOutputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.util.List;


public class Extraction {

    ProgressDialog progressDialog;

    public Extraction(List<ResolveInfo> apps, String publicSourceDir, String apkname, Context context) {
        progressDialog = new ProgressDialog(context);
        progressDialog.setMessage("Extracting");
        progressDialog.setProgressStyle(ProgressDialog.STYLE_SPINNER);
        progressDialog.setIndeterminate(true);
        progressDialog.show();
        BufferedInputStream bufferedInputStream = null;
        BufferedOutputStream bufferedOutputStream = null;
        try {
            File file = new File(publicSourceDir);
            File file1 = new File(Environment.getExternalStorageDirectory().toString() + "/Extracted APK");

            if (!file1.exists())
                file1.mkdirs();

            file1 = new File(file1.getPath() + "/" + apkname + ".apk");
            if (!file1.exists())
                file1.createNewFile();


            bufferedInputStream = new BufferedInputStream(new FileInputStream(file));
            bufferedOutputStream = new BufferedOutputStream(new FileOutputStream(file1));

            byte[] buf = new byte[1024];
            int len;
            while ((len = bufferedInputStream.read(buf)) > 0) {
                bufferedOutputStream.write(buf, 0, len);
            }
            Thread.sleep(1000);
            progressDialog.dismiss();

            Toast.makeText(context, "Apk Extracted", Toast.LENGTH_LONG).show();
            bufferedInputStream.close();
            bufferedOutputStream.close();

        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        } catch (InterruptedException e) {
            e.printStackTrace();
        } finally {
            try {
                bufferedInputStream.close();
                bufferedOutputStream.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
    }
}

Answer 1

您需要将长期运行的工作放在单独的Thread或asyncTask中

因为只有在您长时间运行的代码完成后才更新UI，然后才调用show / dismiss。 那就是为什么您只看到最终结果的原因：对话框已关闭

请参见示例（引自此处： Android：ProgressDialog未显示 ）：

做类似的事情：

 public void doBackup(View view) throws IOException{ final ProgressDialog pd = new ProgressDialog(this); pd.setProgressStyle(ProgressDialog.STYLE_SPINNER); pd.setMessage("Running backup. Do not unplug drive"); pd.setIndeterminate(true); pd.setCancelable(false); pd.show(); Thread mThread = new Thread() { @Override public void run() { File source = new File("/mnt/extSdCard/DirectEnquiries"); File dest = new File("/mnt/UsbDriveA/Backup"); copyDirectory(source, dest); pd.dismiss(); } }; mThread.start(); } 

也是这里： 执行任务时不显示ProgressDialog