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：

<?xml version="1.0" encoding="utf-8"?><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"    tools:context="com.example.administrator.jreduch09.InnerIOActivity"><EditText    android:layout_width="match_parent"    android:layout_height="wrap_content"    android:hint="请输入内容"    android:id="@+id/content"    />    <Button        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:text="保存"        android:id="@+id/save"        android:layout_below="@+id/content"        android:layout_alignParentEnd="true" />    <Button        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:text="读取"        android:id="@+id/read"        android:layout_below="@+id/content"        android:layout_alignParentStart="true" />    <TextView        android:layout_width="match_parent"        android:layout_height="50dp"        android:layout_below="@+id/read"        android:id="@+id/show"        />    <Button        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:id="@+id/delete"        android:text="删除"        android:layout_below="@+id/content"        android:layout_centerHorizontal="true" /></RelativeLayout>

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：

<?xml version="1.0" encoding="utf-8"?><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"    tools:context="com.example.administrator.jreduch09.ReadRawAndAssetsActivity"><Button    android:layout_width="wrap_content"    android:layout_height="wrap_content"    android:id="@+id/raw"    android:text="读取raw"    />    <Button        android:layout_width="wrap_content"        android:layout_height="wrap_content"        android:id="@+id/assets"        android:text="读取assets"        android:layout_alignParentTop="true"        android:layout_alignParentEnd="true" />    <TextView        android:layout_width="match_parent"        android:layout_height="50dp"        android:id="@+id/show"        android:layout_below="@+id/assets"        /></RelativeLayout>

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：