我正在android studio中制作应用程序，在我的应用程序中我添加了该功能，如果用户第二次单击按钮，则该按钮将被禁用并将按钮的状态保存在sharedprefernce中，并且如果用户关闭应用程序并且再次打开应用程序，然后显示保存按钮状态(如果按钮被禁用，则显示禁用按钮，否则显示启用状态)。我在代码中放入了很多sharedprefences的代码，但是每次都会出现空对象引用。下面给出了我的代码，我将共享首选项代码放在此按钮上，但是如何呢？
java:
button.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
counrClick = counrClick + 1;
if (counrClick == 1) {
downloadManager = (DownloadManager) getSystemService(Context.DOWNLOAD_SERVICE);
Uri uri = Uri.parse("Url");
DownloadManager.Request request = new DownloadManager.Request(uri);
request.setAllowedNetworkTypes(DownloadManager.Request.NETWORK_WIFI | DownloadManager.Request.NETWORK_MOBILE);
request.setAllowedOverRoaming(false);
request.setTitle("" + "" + "");
request.setDescription("Downloading " + "" + "");
request.setVisibleInDownloadsUi(true);
request.setNotificationVisibility(DownloadManager.Request.VISIBILITY_VISIBLE_NOTIFY_COMPLETED);
Long reference = downloadManager.enqueue(request);
request.setDestinationInExternalPublicDir(Environment.DIRECTORY_DOWNLOADS, "/" + "filename");
refid = downloadManager.enqueue(request);
Log.e("OUT", "" + refid);
if (counrClick == 2) {
button.setEnabled(false);
}
}
}
});
最佳答案
请引用下面的代码。请记住，您可以使用首选项名称 ("MY_PREF") 和键名称 ("DOWNLOAD_BUTTON_STATUS") 来更改应用程序中其他任何位置的首选项。您甚至可以创建一个单独的类来控制应用程序中的所有首选项。
private SharedPreferences sharedPreferences;
private Button btn_download_one, btn_download_two, btn_download_three, btn_download_four;
private final String DOWNLOAD_BUTTON_STATUS_KEY_ONE = "DOWNLOAD_BUTTON_STATUS_ONE";
private final String DOWNLOAD_BUTTON_STATUS_KEY_TWO = "DOWNLOAD_BUTTON_STATUS_TWO";
private final String DOWNLOAD_BUTTON_STATUS_KEY_THREE = "DOWNLOAD_BUTTON_STATUS_THREE";
private final String DOWNLOAD_BUTTON_STATUS_KEY_FOUR = "DOWNLOAD_BUTTON_STATUS_FOUR";
private int clickCountOne = 0, clickCountTwo = 0, clickCountThree = 0, clickCountFour = 0;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main);
btn_download_one = findViewById(R.id.button1);
btn_download_two = findViewById(R.id.button2);
btn_download_three = findViewById(R.id.button3);
btn_download_four = findViewById(R.id.button4);
sharedPreferences = getSharedPreferences("MY_PREF", 0);
btn_download_one.setEnabled(getDownloadButtonStatusPref(DOWNLOAD_BUTTON_STATUS_KEY_ONE));
btn_download_two.setEnabled(getDownloadButtonStatusPref(DOWNLOAD_BUTTON_STATUS_KEY_TWO));
btn_download_three.setEnabled(getDownloadButtonStatusPref(DOWNLOAD_BUTTON_STATUS_KEY_THREE));
btn_download_four.setEnabled(getDownloadButtonStatusPref(DOWNLOAD_BUTTON_STATUS_KEY_FOUR));
btn_download_one.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
//... some code
clickCountOne++;
if (clickCountOne == 2)
changeDownloadButtonStatusPref(DOWNLOAD_BUTTON_STATUS_KEY_ONE, false);
}
});
btn_download_two.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
//... some code
clickCountTwo++;
if (clickCountTwo == 2)
changeDownloadButtonStatusPref(DOWNLOAD_BUTTON_STATUS_KEY_TWO, false);
}
});
btn_download_three.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
//... some code
clickCountThree++;
if (clickCountThree == 2)
changeDownloadButtonStatusPref(DOWNLOAD_BUTTON_STATUS_KEY_THREE, false);
}
});
btn_download_four.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
//... some code
clickCountFour++;
if (clickCountFour == 2)
changeDownloadButtonStatusPref(DOWNLOAD_BUTTON_STATUS_KEY_FOUR, false);
}
});
}
private void changeDownloadButtonStatusPref(String key, boolean status) {
sharedPreferences.edit().putBoolean(key, status).apply();
switch (key) {
case DOWNLOAD_BUTTON_STATUS_KEY_ONE:
btn_download_one.setEnabled(status);
clickCountOne = 0;
break;
case DOWNLOAD_BUTTON_STATUS_KEY_TWO:
btn_download_two.setEnabled(status);
clickCountTwo = 0;
break;
case DOWNLOAD_BUTTON_STATUS_KEY_THREE:
btn_download_three.setEnabled(status);
clickCountThree = 0;
break;
case DOWNLOAD_BUTTON_STATUS_KEY_FOUR:
btn_download_four.setEnabled(status);
clickCountFour = 0;
break;
}
}
private boolean getDownloadButtonStatusPref(String key) {
return sharedPreferences.getBoolean(key, true);
}
关于java - 保存按钮状态(启用和禁用)，我们在Stack Overflow上找到一个类似的问题： https://stackoverflow.com/questions/56785911/