如何在android中实现下载位置的首选项活动

public class DownloadSettingsActivity extends PreferenceActivity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        addPreferencesFromResource(R.xml.download_settings);
    }
}

<PreferenceScreen xmlns:android="http://schemas.android.com/apk/res/android">
    <PreferenceCategory android:title="Download Settings">
        <ListPreference
            android:key="download_location"
            android:title="Download Location"
            android:summary="Select the location to save downloaded files"
            android:entries="@array/download_locations"
            android:entryValues="@array/download_locations_values"
            android:defaultValue="0" />
    </PreferenceCategory>
</PreferenceScreen>

<resources>
    <string-array name="download_locations">
        <item>Internal Storage</item>
        <item>External Storage</item>
    </string-array>
    <string-array name="download_locations_values">
        <item>internal</item>
        <item>external</item>
    </string-array>
</resources>

public class DownloadSettingsActivity extends PreferenceActivity {
    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        addPreferencesFromResource(R.xml.download_settings);

        ListPreference downloadLocationPreference = (ListPreference) findPreference("download_location");
        downloadLocationPreference.setOnPreferenceChangeListener(new Preference.OnPreferenceChangeListener() {
            @Override
            public boolean onPreferenceChange(Preference preference, Object newValue) {
                // 保存用户选择的下载位置
                SharedPreferences sharedPreferences = PreferenceManager.getDefaultSharedPreferences(getApplicationContext());
                SharedPreferences.Editor editor = sharedPreferences.edit();
                editor.putString("download_location", (String) newValue);
                editor.apply();
                return true;
            }
        });
    }
}

SharedPreferences sharedPreferences = PreferenceManager.getDefaultSharedPreferences(getApplicationContext());
String downloadLocation = sharedPreferences.getString("download_location", "internal");

if (downloadLocation.equals("internal")) {
    // 保存到内部存储
    File file = new File(getFilesDir(), "downloaded_file.txt");
    // 下载文件到file
} else if (downloadLocation.equals("external")) {
    // 保存到外部存储
    File file = new File(Environment.getExternalStorageDirectory(), "downloaded_file.txt");
    // 下载文件到file
}