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();        }    }}

<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>

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();        }    }}

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);        }            }    }

<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>

<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>