为什么 stringbuffer 在这段代码中不起作用？ [关闭]

Question

我要xml.file

第一：

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    android:paddingBottom="@dimen/activity_vertical_margin"
    android:paddingLeft="@dimen/activity_horizontal_margin"
    android:paddingRight="@dimen/activity_horizontal_margin"
    android:paddingTop="@dimen/activity_vertical_margin"
    tools:context=".Text1" >

    <Button
        android:id="@+id/button1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentTop="true"
        android:layout_centerHorizontal="true"
        android:layout_marginTop="36dp"
        android:text="Button1" />



</RelativeLayout>

秒：

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="match_parent"
    android:layout_height="match_parent" >

    <TextView
        android:id="@+id/textView1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentRight="true"
        android:layout_alignParentTop="true"
        android:layout_marginRight="20dp"
        android:layout_marginTop="28dp"
        android:text="TextView" />

</RelativeLayout> 

我在资产文件夹中有一个 txt.file，其名称为 12.txt 我想当我在第一个 xml.file 中按下 button1 时，我会转到第二个 xml.file 和 textview，并在资产文件夹中设置我的 txt.file

代码是：

public class Text2 extends Activity {
private TextView txt;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        // TODO Auto-generated method stub
        super.onCreate(savedInstanceState);
        setContentView(R.layout.text2);
        txt=(TextView)findViewById(R.id.textView1);


        FileInputStream fis=null;
        final StringBuffer buffer= new StringBuffer();

        try {
            fis = openFileInput("12.txt");
            DataInputStream dataIO = new DataInputStream(fis);
            String strLine = null;

            if ((strLine = dataIO.readLine()) != null) {
                buffer.append(strLine);
            }

            dataIO.close();
            fis.close();
        }
        catch  (Exception e) {  
        }
        txt.setText(buffer.toString());





    }





}

为什么它不起作用？ 当我按下 button1 时，我转到第二个 xml.file 但 textview 为空！！！

Answer 1

试试这个..

    txt=(TextView)findViewById(R.id.textView1);        

    AssetManager assetManager = getAssets();
    InputStream inputStream = null;
    try {
         inputStream = assetManager.open("12.txt");
         BufferedReader r = new BufferedReader(new InputStreamReader(inputStream));
         StringBuilder total = new StringBuilder();
         String line;
         while ((line = r.readLine()) != null) {
              total.append(line);
         }
         txt.setText(total.toString());
    }
    catch (IOException e){
         e.printStackTrace();
    }

Answer 2

像这样使用代码：

          FileInputStream fstream = new FileInputStream(Environment.getExternalStorageDirectory()+filenames));
          DataInputStream in = new DataInputStream(fstream);
          BufferedReader br = new BufferedReader(new InputStreamReader(in));
          String strLine;
          while ((strLine = br.readLine()) != null)   
          {
              arrayOfarray.add(strLine);
          }

Answer 3

我最好的猜测是程序的运行目录不是你想象的那样，openFileInput() 会抛出一个 IOException，因为它找不到 12.txt。你的 catch-all-do-nothing 块可能隐藏了一个错误。您可能想要记录异常并中止。如果您不关心导致程序崩溃的异常情况，可以使用以下廉价技巧来获取回溯：

catch(Exception e)
{
    throw(new RuntimeException(e));
}

当我编写的代码应该是高标准项目的一部分（而不是一次性实验或其他东西），或者其他人会看到时，我会创建 MyIOException，它是 RuntimeException 的子类（可能通过中间 MyRuntimeException) 并且有一个 IOException 成员，然后当我捕获一个 IOException 时我会抛出一个包装好的 MyIOException，它的好处是让我的调用者使用基于类的异常调度。

Answer 4

Try this code. it works for me. so it will help you.

package com.example.answerquestion;

import java.io.DataInputStream;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileWriter;
import java.io.PrintWriter;

import android.app.Activity;
import android.os.Bundle;
import android.view.View;
import android.view.View.OnClickListener;
import android.widget.Button;

public class MainActivity extends Activity {

    Button btn;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.main);
        btn = (Button) findViewById(R.id.btn1);
        btn.setOnClickListener(new OnClickListener() {

            @Override
            public void onClick(View v) {
                File dir = new File(getFilesDir().getAbsolutePath());
                try{
                    PrintWriter out = new PrintWriter(new FileWriter(dir + "/test.txt"));
                    for (int i = 0; i < 20; i++) {
                        out.println("omg");
                    }
                    out.close();
                    File file = new File(getFilesDir().getAbsolutePath(), "/test.txt");
                    FileInputStream in = new FileInputStream(file);
                  //  FileInputStream fis=null;
                    final StringBuffer buffer= new StringBuffer();

                       // fis = openFileInput("12.txt");
                        DataInputStream dataIO = new DataInputStream(in);
                        String strLine = null;

                        if ((strLine = dataIO.readLine()) != null) {
                            buffer.append(strLine);
                        }

                        dataIO.close();
                        in.close();
                        System.out.print(buffer.toString());
                    }
                    catch  (Exception e) {  
                    }

                }

        });
    }

}

Answer 5

对不起哥们！！ 我再次编辑它，现在它将完美运行！

 public class Text2 extends Activity {
        private TextView txt;

            @Override
            protected void onCreate(Bundle savedInstanceState) {
                // TODO Auto-generated method stub
                super.onCreate(savedInstanceState);
                setContentView(R.layout.text2);
                txt=(TextView)findViewById(R.id.textView1);  
         String mLine ="";  
        try {
                BufferedReader reader = new BufferedReader(
                    new InputStreamReader(getAssets().open("12.txt")));

                // do reading, usually loop until end of file reading  
                mLine = reader.readLine();


                reader.close();
            } catch (IOException e) {
                //log the exception
            }
            txt.setText(mLine)

         }





        }