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法學如何在Android中使用執行時許可權列出SD卡中的檔案？
此示例演示如何在Android中使用執行時許可權列出SD卡中的檔案。
步驟1 - 在Android Studio中建立一個新專案，轉到檔案⇒新建專案，並填寫所有必需的詳細資訊以建立新專案。
步驟2 - 將以下程式碼新增到res/layout/activity_main.xml。
<?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>在上面的程式碼中，我們使用了列表檢視和按鈕。當用戶點選按鈕時，它將從外部儲存獲取資料並將資料新增到列表檢視。
步驟3 - 將以下程式碼新增到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;
}
}
}步驟4 - 將以下程式碼新增到manifest.xml
<?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>
讓我們嘗試執行您的應用程式。我假設您已將您的實際Android移動裝置連線到您的計算機。要從Android Studio執行應用程式，請開啟您的專案活動檔案之一，然後單擊工具欄中的執行play.jpg圖示。選擇您的移動裝置作為選項，然後檢查您的移動裝置，它將顯示您的預設螢幕 -
在上述結果中，單擊讀取按鈕以顯示外部儲存目錄檔案的列表，如下所示 -
點選 這裡 下載專案程式碼
更新於：2019年7月30日
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