安卓学习-数据存储与IO-File存储

1.data目录下

MainActivity.java

public class MainActivity extends Activity implements OnClickListener {

    EditText editText1;
    TextView textView3;
    SharedPreferences pre;
    Editor editor;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        editText1 = (EditText) findViewById(R.id.editText1);
        textView3 = (TextView) findViewById(R.id.textView3);


        Button btn1 = (Button) findViewById(R.id.button1);
        Button btn2 = (Button) findViewById(R.id.button2);
        btn1.setOnClickListener(this);
        btn2.setOnClickListener(this);
    }

    public void onClick(View v) {
        try {
            if (v == findViewById(R.id.button1)) {

                String str=editText1.getText().toString();
                FileOutputStream out = openFileOutput("test.bin",Context.MODE_PRIVATE);
                out.write(str.getBytes());
                out.close();
            } else if (v == findViewById(R.id.button2)) {
                FileInputStream in=openFileInput("test.bin");
                int len=in.available();
                byte[] bytes=new byte[len];
                in.read(bytes);
                in.close();
                
                textView3.setText(new String(bytes));
            }
        } catch (Exception e) {
            // TODO 自动生成的 catch 块
            e.printStackTrace();
        }
    }
}

View Code

activity_main.xml

<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="${relativePackage}.${activityClass}" >

    <TextView
        android:id="@+id/textView1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignBaseline="@+id/editText1"
        android:layout_alignBottom="@+id/editText1"
        android:layout_alignParentLeft="true"
        android:text="姓名"
        android:textAppearance="?android:attr/textAppearanceLarge" />

    <EditText
        android:id="@+id/editText1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentTop="true"
        android:layout_marginLeft="15dp"
        android:layout_marginTop="15dp"
        android:layout_toRightOf="@+id/textView1"
        android:ems="10" >

        <requestFocus />
    </EditText>

    <Button
        android:id="@+id/button1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentLeft="true"
        android:layout_below="@+id/editText1"
        android:layout_marginTop="22dp"
        android:text="写入" />

    <Button
        android:id="@+id/button2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentLeft="true"
        android:layout_below="@+id/button1"
        android:layout_marginTop="36dp"
        android:text="读取" />

    <TextView
        android:id="@+id/textView2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignBaseline="@+id/button2"
        android:layout_alignBottom="@+id/button2"
        android:layout_marginLeft="11dp"
        android:layout_toRightOf="@+id/button2"
        android:text="值："
        android:textAppearance="?android:attr/textAppearanceLarge" />

    <TextView
        android:id="@+id/textView3"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignBaseline="@+id/textView2"
        android:layout_alignBottom="@+id/textView2"
        android:layout_centerHorizontal="true"
        android:textAppearance="?android:attr/textAppearanceLarge" />

</RelativeLayout>

View Code

2.SD卡目录下

界面和上面一样

添加权限

<uses-permission android:name="android.permission.MOUNT_UNMOUNT_FILESYSTEMS"/>
<uses-permission android:name="android.permission.WRITE_EXTERNAL_STORA"/>

MainActivity.java

public class MainActivity extends Activity implements OnClickListener {

    EditText editText1;
    TextView textView3;
    SharedPreferences pre;
    Editor editor;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        editText1 = (EditText) findViewById(R.id.editText1);
        textView3 = (TextView) findViewById(R.id.textView3);


        Button btn1 = (Button) findViewById(R.id.button1);
        Button btn2 = (Button) findViewById(R.id.button2);
        btn1.setOnClickListener(this);
        btn2.setOnClickListener(this);
    }

    public void onClick(View v) {
        try {
            if (v == findViewById(R.id.button1)) {
                //判断是否安装了SD卡
                if(Environment.getExternalStorageState().equals(Environment.MEDIA_MOUNTED)){
                    //获取SD卡路径 /storage/emulated/0
                    File sdCardDir=Environment.getExternalStorageDirectory();
                    File file=new File(sdCardDir.getCanonicalPath()+"/test.txt");
                    //判断文件是否存在，不存在则创建
                    if(!file.exists()){
                        file.createNewFile();
                    }
                    String str=editText1.getText().toString();
                    //构建out写入数据
                    FileOutputStream out =new FileOutputStream(file);
                    out.write(str.getBytes());
                    out.close();
                }else{
                    Toast.makeText(MainActivity.this, "没有发现SD卡", Toast.LENGTH_SHORT).show();
                }
            } else if (v == findViewById(R.id.button2)) {
                FileInputStream in=new FileInputStream(Environment.getExternalStorageDirectory().getCanonicalPath()+"/test.txt");
                int len=in.available();
                byte[] bytes=new byte[len];
                in.read(bytes);
                in.close();
                
                textView3.setText(new String(bytes));
            }
        } catch (Exception e) {
            // TODO 自动生成的 catch 块
            e.printStackTrace();
        }
    }
}

View Code

3.获取SD卡目录小程序

点击文件加后，进入下一层目录，点击“父目录”返回上一层

MainActivity.java

public class MainActivity extends Activity {

    //当前位置路径
    String cutFile;
    
    TextView textView2;
    ListView lv;
    SimpleAdapter adapter;
    
    ArrayList<HashMap<String,Object>> fileList=new ArrayList<HashMap<String,Object>>();
    
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);
        
        textView2=(TextView)findViewById(R.id.textView2);

        try {
            //获取SD卡路径，并保存下来
            cutFile=Environment.getExternalStorageDirectory().getCanonicalPath();
            textView2.setText(cutFile);
        } catch (IOException e) {
            // TODO 自动生成的 catch 块
            e.printStackTrace();
        }
        
        listFile(cutFile);
        
        adapter=new SimpleAdapter(MainActivity.this, 
                fileList, R.layout.item, 
                new String[]{"name","date","icon"}, new int[]{R.id.textView1,R.id.textView2,R.id.imageView1});

        lv=(ListView)findViewById(R.id.listView1);
        lv.setAdapter(adapter);
        
        lv.setOnItemClickListener(new OnItemClickListener() {

            @Override
            public void onItemClick(AdapterView<?> paramAdapterView,
                    View paramView, int paramInt, long paramLong) {
                //点击时，获取当前点击的项信息
                HashMap<String,Object> map=fileList.get(paramInt);
                String name=map.get("name")+"";
                String path=map.get("path")+"";
                File file=new File(path);
                //判断是否是目录
                if(file.isDirectory()){
                    //是否是回到上一层
                    if(name.equals("..")){
                        //获取上一层目录
                        File file11=new File(path);
                        listFile(file11.getParentFile().getPath());
                    }else{
                        listFile(path);
                    }
                    
                    //刷新
                    adapter.notifyDataSetChanged();                    
                }
            }
        });
    }
    
    
    public void listFile(String path){
        cutFile=path;
        textView2.setText(cutFile);
        
        //清空
        fileList.clear();
        //第一层目录，不添加父目录项
        try {
            if(!path.equals(Environment.getExternalStorageDirectory().getCanonicalPath())){
                HashMap<String,Object> map1=new HashMap<String,Object>();
                map1.put("name", "..");
                map1.put("date", "父目录");
                map1.put("icon", R.drawable.folder);
                map1.put("path", cutFile);
                fileList.add(map1);
            }
        } catch (IOException e) {
            // TODO 自动生成的 catch 块
            e.printStackTrace();
        }
        
        File sdCardDir=new File(path);        
        File[] list=sdCardDir.listFiles();
        for(int i=0;i<list.length;i++){
            File file=list[i];
            HashMap<String,Object> map=new HashMap<String,Object>();
            //获取文件名
            map.put("name", file.getName());
            //获取修改时间
            Long time =file.lastModified();
            Calendar cd = Calendar.getInstance();
            cd.setTimeInMillis(time);
            Date tasktime=cd.getTime();  
            //设置日期输出的格式  
            SimpleDateFormat df=new SimpleDateFormat("yyyy年MM月dd日  HH时mm分ss秒");  
            //格式化输出   
            map.put("date", df.format(tasktime));
            //判断是否是目录
            if(file.isDirectory()){
                map.put("icon", R.drawable.folder);
            }else{
                map.put("icon", R.drawable.invoice);
            }
            map.put("path",cutFile+"/"+file.getName());
            fileList.add(map);
        }
        
    }

    
}

View Code

item.xml

<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    android:layout_width="fill_parent"
    android:layout_height="fill_parent" android:padding="10dp">

    <TextView
        android:id="@+id/textView2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignLeft="@+id/textView1"
        android:layout_alignParentRight="true"
        android:layout_below="@+id/textView1"
        android:text="创建时间"
        android:textAppearance="?android:attr/textAppearanceSmall" />

    <TextView
        android:id="@+id/textView1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignTop="@+id/imageView1"
        android:layout_marginLeft="15dp"
        android:layout_toRightOf="@+id/imageView1"
        android:text="文件名"
        android:textAppearance="?android:attr/textAppearanceSmall" />

    <ImageView
        android:id="@+id/imageView1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentLeft="true"
        android:layout_alignParentTop="true"
        android:layout_marginLeft="19dp"
        android:src="@drawable/folder" />

</RelativeLayout>

View Code

activity_main.xml

<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="${relativePackage}.${activityClass}" >

    <ListView
        android:id="@+id/listView1"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_alignParentLeft="true"
        android:layout_below="@+id/textView1" >

    </ListView>

    <TextView
        android:id="@+id/textView1"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentLeft="true"
        android:layout_alignParentTop="true"
        android:text="当前路径:"
        android:textAppearance="?android:attr/textAppearanceSmall" />

    <TextView
        android:id="@+id/textView2"
        android:layout_width="wrap_content"
        android:layout_height="wrap_content"
        android:layout_alignParentTop="true"
        android:layout_marginLeft="14dp"
        android:layout_toRightOf="@+id/textView1"
        android:text="当前路径"
        android:textAppearance="?android:attr/textAppearanceSmall" />

</RelativeLayout>

View Code

两个图片资源

folder.png

invoice.png

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原文地址：https://www.cnblogs.com/weijj/p/4201128.html