如何在 Android 中使用运行时权限列出 SD 卡中的文件?
androidmobile developmentapps/applications
本示例演示如何在 Android 中使用运行时权限列出 SD 卡中的文件。
步骤 1 - 在 Android Studio 中创建一个新项目，依次点击"文件">"新建项目"，并填写所有必需信息以创建一个新项目。
步骤 2 - 将以下代码添加到 res/layout/activity_main.xml 文件中。
<?xml version = "1.0" encoding = "utf-8"?>
<LinearLayout 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 = ".MainActivity"
android:orientation = "vertical">
<Button
android:id = "@+id/read"
android:text = "read"
android:layout_width = "wrap_content"
android:layout_height = "wrap_content" />
<ListView
android:id = "@+id/list"
android:layout_width = "match_parent"
android:layout_height = "wrap_content"></ListView>
</LinearLayout>
上面的代码中使用了列表视图和按钮。当用户点击按钮时，它会从外部存储获取数据并将其添加到列表视图中。
步骤 3 − 将以下代码添加到 src/MainActivity.java
package com.example.andy.myapplication;
import android.content.pm.PackageManager;
import android.os.Build;
import android.os.Bundle;
import android.os.Environment;
import android.support.v4.app.ActivityCompat;
import android.support.v4.content.ContextCompat;
import android.support.v7.app.AppCompatActivity;
import android.util.Log;
import android.view.View;
import android.widget.ArrayAdapter;
import android.widget.Button;
import android.widget.ListView;
import android.widget.Toast;
import java.io.File;
import java.util.ArrayList;
public class MainActivity extends AppCompatActivity {
private static final int PERMISSION_REQUEST_CODE = 100;
Button read;
ArrayList<String> myList;
ListView listview;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
listview = findViewById(R.id.list);
read = findViewById(R.id.read);
myList = new ArrayList<>();
read.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
String state = Environment.getExternalStorageState();
if (Environment.MEDIA_MOUNTED.equals(state)) {
if (Build.VERSION.SDK_INT > = 23) {
if (checkPermission()) {
File dir = new File(Environment.getExternalStorageDirectory().getAbsolutePath() + "/");
if (dir.exists()) {
Log.d("path", dir.toString());
File list[] = dir.listFiles();
for (int i = 0; i < list.length; i++) {
myList.add(list[i].getName());
}
ArrayAdapter arrayAdapter = new ArrayAdapter(MainActivity.this, android.R.layout.simple_list_item_1, myList);
listview.setAdapter(arrayAdapter);
}
} else {
requestPermission(); // Code for permission
}
} else {
File dir = new File(Environment.getExternalStorageDirectory().getAbsolutePath() + "/");
if (dir.exists()) {
Log.d("path", dir.toString());
File list[] = dir.listFiles();
for (int i = 0; i < list.length; i++) {
myList.add(list[i].getName());
}
ArrayAdapter arrayAdapter = new ArrayAdapter(MainActivity.this, android.R.layout.simple_list_item_1, myList);
listview.setAdapter(arrayAdapter);
}
}
}
}
});
}
private boolean checkPermission() {
int result = ContextCompat.checkSelfPermission(MainActivity.this, android.Manifest.permission.READ_EXTERNAL_STORAGE);
if (result = = PackageManager.PERMISSION_GRANTED) {
return true;
} else {
return false;
}
}
private void requestPermission() {
if (ActivityCompat.shouldShowRequestPermissionRationale(MainActivity.this, android.Manifest.permission.READ_EXTERNAL_STORAGE)) {
Toast.makeText(MainActivity.this, "Write External Storage permission allows us to read files.
Please allow this permission in App Settings.", Toast.LENGTH_LONG).show();
} else {
ActivityCompat.requestPermissions(MainActivity.this, new String[]
{android.Manifest.permission.READ_EXTERNAL_STORAGE}, PERMISSION_REQUEST_CODE);
}
}
@Override
public void onRequestPermissionsResult(int requestCode, String permissions[], int[] grantResults) {
switch (requestCode) {
case PERMISSION_REQUEST_CODE:
if (grantResults.length > 0 && grantResults[0] = = PackageManager.PERMISSION_GRANTED) {
Log.e("value", "Permission Granted, Now you can use local drive .");
} else {
Log.e("value", "Permission Denied, You cannot use local drive .");
}
break;
}
}
}
步骤 4将以下代码添加到 manifest.xml 文件中
<?xml version = "1.0" encoding = "utf-8"?> <manifest xmlns:android = "http://schemas.android.com/apk/res/android" package = "com.example.andy.myapplication"> <uses-permission android:name = "android.permission.WRITE_EXTERNAL_STORAGE"/> <uses-permission android:name = "android.permission.READ_EXTERNAL_STORAGE"/> <application android:allowBackup = "true" android:icon = "@mipmap/ic_launcher" android:label = "@string/app_name" android:roundIcon = "@mipmap/ic_launcher_round" android:supportsRtl = "true" android:theme = "@style/AppTheme"> <activity android:name = ".MainActivity"> <intent-filter> <action android:name = "android.intent.action.MAIN" /> <category android:name = "android.intent.category.LAUNCHER" /> </intent-filter> </activity> </application> </manifest>
让我们尝试运行您的应用程序。我假设您已将 Android 移动设备连接到计算机。要从 Android Studio 运行应用程序，请打开项目中的一个 Activity 文件，然后单击工具栏中的"运行 play.jpg"图标。选择您的移动设备作为选项，然后检查您的移动设备，它将显示您的默认屏幕。
在上面的结果中，单击"读取"按钮以显示外部存储目录文件列表，如下所示。
