ANDROID笔记:File操作

package com.example.android_file;

import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.PrintStream;

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

public class MainActivity extends Activity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        Button button = (Button) findViewById(R.id.button1);
        button.setOnClickListener(new OnClickListener() {

            @Override
            public void onClick(View arg0) {
                // write("测试字符串");
                writeSDFile("测试字符串");
            }
        });
        Button button2 = (Button) findViewById(R.id.button2);
        button2.setOnClickListener(new OnClickListener() {

            @Override
            public void onClick(View arg0) {
                // Toast.makeText(MainActivity.this, read(), 200).show();
                Toast.makeText(MainActivity.this, readSDFile(), 200).show();
            }
        });
    }

    /**
     * 向程序作用域文件写入内容,路径:/data/data/com.example.android_file/files
     * 
     * @param content
     */
    private void write(String content) {
        try {
            FileOutputStream fileOutputStream = openFileOutput("file.txt",
                    Activity.MODE_APPEND);
            PrintStream printStream = new PrintStream(fileOutputStream);
            printStream.println(content);
            printStream.close();
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        }

    }

    /**
     * 获取程序作用域文件的内容,路径:/data/data/com.example.android_file/files
     * 
     * @return
     */
    private String read() {
        StringBuffer stringBuffer = new StringBuffer();
        FileInputStream fileInputStream = null;
        try {
            // openFileInput
            fileInputStream = openFileInput("file.txt");
            byte[] bytes = new byte[1024];
            int len = 0;
            while ((len = fileInputStream.read(bytes)) != -1) {
                stringBuffer.append(new String(bytes, "utf-8"));

            }
        } catch (FileNotFoundException e) {
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        } finally {
            try {
                fileInputStream.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }
        return stringBuffer.toString();

    }

    /**
     * 向SD文件写入内容
     * 
     * @param content
     */
    private void writeSDFile(String content) {
        if (Environment.getExternalStorageState().equals(
                Environment.MEDIA_MOUNTED)) {
            try {
                // 获取sd的路径
                String path = Environment.getExternalStorageDirectory()
                        .getCanonicalPath() + "/file.txt";
                FileOutputStream fileOutputStream = new FileOutputStream(path,
                        true);// true:追加方式
                PrintStream printStream = new PrintStream(fileOutputStream);
                printStream.println(content);
                printStream.close();
            } catch (IOException e) {
                e.printStackTrace();
            }
        }

    }

    /**
     * 获取SD卡文件内容
     * 
     * @return
     */
    private String readSDFile() {
        StringBuffer stringBuffer = new StringBuffer();
        FileInputStream fileInputStream = null;
        if (Environment.getExternalStorageState().equals(
                Environment.MEDIA_MOUNTED)) {
            // 获取sd的路径
            try {
                String path = Environment.getExternalStorageDirectory()
                        .getCanonicalPath() + "/file.txt";
                fileInputStream = new FileInputStream(path);
                byte[] bytes = new byte[1024];
                int len = 0;
                while ((len = fileInputStream.read(bytes)) != -1) {
                    stringBuffer.append(new String(bytes, "utf-8"));
                }
            } catch (IOException e) {
                e.printStackTrace();
            } finally {
                try {
                    fileInputStream.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }

        }
        return stringBuffer.toString();
    }
}

openFileOutput和openFileInput 只能用于/data/data/包名/files 下文件的操作