我在 android studio 中制作應用程序，在我的應用程序中我添加了功能，如果用戶第二次單擊按鈕，則按鈕被禁用并將按鈕的狀態保存在 sharedpreference 中，如果用戶關閉應用程序并再次打開app 然后顯示保存按鈕狀態（如果按鈕被禁用，則顯示禁用按鈕，否則顯示啟用狀態）。我的代碼里放了很多sharedprefences的代碼，但是每次都會出現null object reference。我的代碼在下面給出，我把共享首選項代碼放在這個按鈕上，但是怎么做呢？爪哇： 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); } } } });
3 回答
UYOU
TA貢獻1878條經驗 獲得超4個贊
請參考下面的代碼。請記住，您可以使用首選項名稱 ( "MY_PREF") 和鍵名 ( "DOWNLOAD_BUTTON_STATUS") 來更改應用程序中其他任何位置的首選項。您甚至可以創建一個單獨的類來控制應用程序中的所有首選項。
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);
}
千巷貓影
TA貢獻1829條經驗 獲得超7個贊
//在按鈕點擊時添加此代碼
SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(this);
prefs.edit().putString("enabled", "").apply();
//在OnCreate/OncreateView方法中添加這段代碼
String statusLocked1 = prefs.getString("enabled","");
if(statusLocked1.equals("enabled")){
//enable the button
}else{
//disbale the button
}
SMILET
TA貢獻1796條經驗 獲得超4個贊
試試這個，如果它之前被點擊過兩次，它會在你下次運行你的活動時禁用按鈕；
Button button;
SharedPreferences preferences;
boolean firstclick = true;
@Override
protected void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_main2);
// SharePrefs
preferences = getSharedPreferences("yourprefsname", 0);
firstclick = preferences.getBoolean("countclick", false);
button = findViewById(R.id.yourbutton);
//disables if it is clicked twice
if (!firstclick){
button.setEnabled(false);
}
button.setOnClickListener(new View.OnClickListener() {
@Override
public void onClick(View v) {
if (firstclick) {
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);
else{
//edit prefs
preferences.edit().putBoolean("countclick",firstclick).apply();
button.setEnabled(false);
}
}
}
});
}
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