Question

当我尝试在模拟器或物理设备上运行时，应用程序无法启动，并显示一条消息，指出应用程序意外停止。只有1个课程和1个活动。我在清单中添加了所需的权限。我正在使用itelliJ IDE。

这是代码

import android.app.Activity;
import android.app.Dialog;
import android.app.ProgressDialog;
import android.os.AsyncTask;
import android.os.Bundle;
import android.os.Environment;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import java.io.*;
import java.net.URL;
import java.net.URLConnection;

public class MyActivity extends Activity {

Button download , view;
static EditText uID , sID;

// Progress Dialog
private ProgressDialog pDialog;
public static final int progress_bar_type = 0;


static String value_sID = sID.getText().toString().trim();
static String value_uID = uID.getText().toString().trim();

private static String file_url = "http://someurl.com"+"/"+value_sID+"/"+value_uID+".pdf"+"/";
String fileName = value_sID+"_"+value_uID;

@Override
public void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.main);

    download = (Button)findViewById(R.id.btn_Download);
    view = (Button)findViewById(R.id.btn_View);

    uID = (EditText)findViewById(R.id.et_uID);
    sID = (EditText)findViewById(R.id.et_sID);

    download.setOnClickListener(new View.OnClickListener() {
        @Override
        public void onClick(View v) {

            new DownloadFileFromURL().execute(file_url);

        }
    });

}

@Override
protected Dialog onCreateDialog(int id) {
    switch (id) {
        case progress_bar_type: // we set this to 0
            pDialog = new ProgressDialog(this);
            pDialog.setMessage("Downloading file. Please wait...");
            pDialog.setIndeterminate(false);
            pDialog.setMax(100);
            pDialog.setProgressStyle(ProgressDialog.STYLE_HORIZONTAL);
            pDialog.setCancelable(true);
            pDialog.show();
            return pDialog;
        default:
            return null;
    }
}

class DownloadFileFromURL extends AsyncTask<String, String, String> {

    @Override
    protected void onPreExecute() {
        super.onPreExecute();
        showDialog(progress_bar_type);
    }

    @Override
    protected String doInBackground(String... f_url) {
        int count;
        try {
            URL url = new URL(f_url[0]);
            URLConnection conection = url.openConnection();
            conection.connect();

            // this will be useful so that you can show a tipical 0-100%
            // progress bar
            int lenghtOfFile = conection.getContentLength();

            // download the file
            InputStream input = new BufferedInputStream(url.openStream(),
                    8192);

            // Output stream
            OutputStream output = new FileOutputStream(Environment
                    .getExternalStorageDirectory().toString()
                    + "/dirs/"+fileName);

            byte data[] = new byte[1024];

            long total = 0;

            while ((count = input.read(data)) != -1) {
                total += count;
                // publishing the progress....
                // After this onProgressUpdate will be called
                publishProgress("" + (int) ((total * 100) / lenghtOfFile));

                // writing data to file
                output.write(data, 0, count);
            }

            // flushing output
            output.flush();

            // closing streams
            output.close();
            input.close();

        } catch (Exception e) {
            Log.e("Error: ", e.getMessage());
        }

        return null;
    }

    protected void onProgressUpdate(String... progress) {
        // setting progress percentage
        pDialog.setProgress(Integer.parseInt(progress[0]));
    }

    @Override
    protected void onPostExecute(String file_url) {
        // dismiss the dialog after the file was downloaded
        dismissDialog(progress_bar_type);

    }

}

}

Answer 1

您正在尝试从EditText中获取文本。但你是在错误的地方做的。

您需要在点击按钮时使用EditText的getText（）。

此外，在初始化之前，请勿从UI Elements获取数据。您正在onCreate（）之外获取数据。

sID.getText().toString().trim()

以上行应该在以下之后：

sID = (EditText)findViewById(R.id.et_sID);

请阅读Android文档。

Android-应用程序意外停止错误而不启动

1 个答案: