Android 数据的读取与写入

完成效果：在文本框中输入数字或文字，点击保存按钮然后再按读取按钮，输入内容显示到按钮下方。

                    在res下新建raw文件，点击读取raw按钮，输入内容显示到按钮下方。

                    新建一个assets，点击读取assets按钮，输入内容显示到按钮下方。

                    点击删除按钮，删除输入内容。

布局1：

代码：

package com.example.administrator.jreduch09;

import android.os.Bundle;
import android.os.Environment;
import android.support.v7.app.AppCompatActivity;
import android.util.Log;
import android.view.View;
import android.widget.Button;
import android.widget.EditText;
import android.widget.TextView;
import android.widget.Toast;
import java.io.BufferedReader;
import java.io.File;
import java.io.FileInputStream;
import java.io.FileNotFoundException;
import java.io.FileOutputStream;
import java.io.IOException;
import java.io.InputStreamReader;

public class SaveToSdCardActivity extends AppCompatActivity {
    private Button save,read,delete;
    private EditText content;
    private TextView show;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_inner_io);
         save= (Button) findViewById(R.id.save);
         read= (Button) findViewById(R.id.read);
         delete= (Button) findViewById(R.id.delete);
         show= (TextView) findViewById(R.id.show);
         content = (EditText) findViewById(R.id.content);
         save.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
            saveFile();
            }
        });
         read.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
               show.setText(readFile());
            }
        });
         delete.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                removeFile();
            }
        });
    }
    //保存文件到SDcard中
    public void saveFile(){
        FileOutputStream fos=null;
        String state= Environment.getExternalStorageState();
        //获取SD卡状态
        if(!state.equals(Environment.MEDIA_MOUNTED)){
            //判断SD卡是否就绪
            Toast.makeText(getBaseContext(),"请检查SD卡",Toast.LENGTH_SHORT).show();
            return;
        }
         File file=Environment.getExternalStorageDirectory();
        //取得SD卡根目录
        try {
            Log.d("===SD卡根目录：",file.getCanonicalPath()+"sd.txt");
            fos=new FileOutputStream(file.getCanonicalPath()+"/sd.txt",true);
            String str=content.getText().toString();
            fos.write(str.getBytes());
            Toast.makeText(getBaseContext(),"保存成功",Toast.LENGTH_SHORT).show();
        } catch (IOException e) {
            e.printStackTrace();
        }finally {
            if(fos!=null){
                try {
                    fos.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
    }
    public String readFile(){
        BufferedReader reader =null;
        FileInputStream fis=null;
        //从SD卡读取文件
        StringBuilder sdb=new StringBuilder();
        String state=Environment.getExternalStorageState();
        if(!state.equals(Environment.MEDIA_MOUNTED)){
            Toast.makeText(getBaseContext(),"SD卡未就绪",Toast.LENGTH_SHORT).show();
            return "";
        }
        File root=Environment.getExternalStorageDirectory();
        try {
            fis=new FileInputStream(root+"/sd.txt");
            reader=new BufferedReader(new InputStreamReader(fis));
            String row="";
            while ((row=reader.readLine())!=null){
                sdb.append(row);
            }
        } catch (FileNotFoundException e) {
            Toast.makeText(this,"文件不存在",Toast.LENGTH_SHORT).show();
            e.printStackTrace();
        } catch (IOException e) {
            e.printStackTrace();
        }finally {
            if(reader!=null){
                try {
                    reader.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
        return sdb.toString();
    }
    public void removeFile(){
        String state=Environment.getExternalStorageState();
        if(!state.equals(Environment.MEDIA_MOUNTED)){
            Toast.makeText(getBaseContext(),"SD卡未就绪",Toast.LENGTH_SHORT).show();
            return;
        }
        File file=Environment.getExternalStorageDirectory();
        File myFile=new File(file,"sd.txt");
        if(myFile.exists()){
            myFile.delete();
            Toast.makeText(this,"文件已删除",Toast.LENGTH_SHORT).show();
        }else{
            Toast.makeText(this,"文件不存在",Toast.LENGTH_SHORT).show();
        }
    }
}

效果展示：

布局2：

代码：

package com.example.administrator.jreduch09;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.View;
import android.widget.Button;
import android.widget.TextView;
import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStream;
import java.io.InputStreamReader;

public class ReadRawAndAssetsActivity extends AppCompatActivity {
    private TextView show;
    private Button raw,assets;
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_read_raw_and_assets);
        raw= (Button) findViewById(R.id.raw);
        assets= (Button) findViewById(R.id.assets);
        show= (TextView) findViewById(R.id.show);
        raw.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
               show.setText(readRaw());
            }
        });
        assets.setOnClickListener(new View.OnClickListener() {
            @Override
            public void onClick(View v) {
                show.setText(readAssets());
            }
        });
    }
    public String readRaw(){
        StringBuilder sbd=new StringBuilder();
        InputStream is=null;
        BufferedReader reader=null;
        is=getResources().openRawResource(R.raw.settings);
        String row="";
        try {
            reader=new BufferedReader(new InputStreamReader(is));
            while ((row=reader.readLine())!=null) {
                sbd.append(row);
            }
        } catch (IOException e) {
            e.printStackTrace();
        }finally {
            if(reader!=null){
                try {
                    reader.close();
                } catch (IOException e) {
                    e.printStackTrace();
                }
            }
        }
        return sbd.toString();
    }
    public String readAssets(){
        StringBuilder sdb=new StringBuilder();
        BufferedReader reader=null;
        try {
            InputStream is=getResources().getAssets().open("city");
            reader=new BufferedReader(new InputStreamReader(is));
            String row="";
            while ((row=reader.readLine())!=null){
                sdb.append(row);
            }
        } catch (IOException e) {
            e.printStackTrace();
        }finally {
            if(reader!=null){
                try {
                    reader.close();
                } catch (IOException e) {

                }
            }
        }
        return sdb.toString();
    }
}

settings中的内容：

1.大家好我是VAE。
2.那是一条神奇的天路啊啊啊。
3.我愿意为你，我愿意为你。
4.如果你对天空向往。

assets中的city的内容：

北京上海广州

效果展示：