如何在android中的文件中附加数据

Question

任何人都可以告诉我如何将数据附加到已经拥有Android数据的文件中吗？

我写了一些代码,但它没有用.这是我的活动:

package updatefile.developer.com.updatefiledemo;

import android.support.v7.app.ActionBarActivity;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.widget.Button;
import android.widget.Toast;

import java.io.BufferedWriter;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileOutputStream;
import java.io.FileWriter;
import java.io.IOException;
import java.io.OutputStreamWriter;
import java.io.PrintStream;
import java.nio.Buffer;

public class MainActivity extends ActionBarActivity {
    Button create,update;
    String data = "This is a sample";
    File file;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        create = (Button)findViewById(R.id.btn_create);
        create.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                File folder = new File("/sdcard/demo");
                folder.mkdirs();
                file = new File("/sdcard/demo/demotext.txt");
                try {
                    FileOutputStream fileinput = new FileOutputStream(file);
                    PrintStream printstream = new PrintStream(fileinput);
                    printstream.print(data+"\n");
                    fileinput.close();
                } catch (Exception e) {
                    Toast.makeText(MainActivity.this,e.getMessage(),Toast.LENGTH_SHORT).show();
                }
            }
        });

        update = (Button)findViewById(R.id.btn_update);
        update.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                if(!file.exists()) {
                    try {
                        file.createNewFile();
                    } catch (Exception e) {
                        Toast.makeText(MainActivity.this,e.getMessage(),Toast.LENGTH_SHORT).show();
                    }
                }

                try {
                    OutputStreamWriter file_writer = new OutputStreamWriter(new FileOutputStream(file,true));
                    BufferedWriter buffered_writer = new BufferedWriter(file_writer);
                    buffered_writer.write("This is a appended text");
                    buffered_writer.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        });
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        // Inflate the menu; this adds items to the action bar if it is present.
        getMenuInflater().inflate(R.menu.menu_main, menu);
        return true;
    }

    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        // Handle action bar item clicks here. The action bar will
        // automatically handle clicks on the Home/Up button, so long
        // as you specify a parent activity in AndroidManifest.xml.
        int id = item.getItemId();

        //noinspection SimplifiableIfStatement
        if (id == R.id.action_settings) {
            return true;
        }

        return super.onOptionsItemSelected(item);
    }
}

Answer 1

FileOutputStream fileinput = new FileOutputStream(file, true);

这是一个简单的错误,因为没有设置追加标志true.只需将其设置为true即可.

默认行为是覆盖文件内容:)

Answer 2

File file = new File(path);
        if (!file.exists()) {
            try {
                file.createNewFile();
            } catch (IOException ioe) {
                ioe.printStackTrace();
            }
        }
        try {
            FileOutputStream fileOutputStream = new FileOutputStream(file);
            OutputStreamWriter writer = new OutputStreamWriter(fileOutputStream);
            writer.append(data);
            writer.close();
            fileOutputStream.close();
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }

Answer 3

你唯一要做的就是添加一个"true" to FileOutputStream像

FileOutputStream fileinput = new FileOutputStream(file,true);

这是文档

构造一个写入文件的新FileOutputStream.如果append为true且文件已存在,则将附加到; 否则会被截断.如果文件不存在,将创建该文件.