Android 数据的读取与写入

比眉伴天荒 2022-09-25 06:27 187阅读 0赞

**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：

**![Center][]  
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：

[Center]: /images/20220718/ffa60112aaf54c8b9baa0d18662dee8f.png