保存按鈕狀態（啟用和禁用）

Question

我在android studio中制作應用程序，在我的應用程序中添加了功能，如果用戶第二次單擊按鈕，則該按鈕被禁用並以共享優先級保存按鈕的狀態，並且如果用戶關閉了該應用程序並再次打開應用程序，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）。 我在代碼中放入了許多共享偏好代碼，但是每次出現空對象引用時。 我的代碼在下面給出，我將共享的首選項代碼放在此按鈕上，但是如何？

Java的：

 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);

                    }


                }
            }

        });

Answer 1

請參考下面的代碼。 並且請記住，您可以使用首選項名稱（ "MY_PREF" ）和鍵名稱（ "DOWNLOAD_BUTTON_STATUS" ）來更改應用程序中其他位置的首選項。 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);
}

Answer 2

//在點擊按鈕時添加此代碼

SharedPreferences prefs = PreferenceManager.getDefaultSharedPreferences(this);
        prefs.edit().putString("enabled", "").apply();

//在OnCreate / OncreateView方法中添加此代碼

  String statusLocked1 =  prefs.getString("enabled","");
    if(statusLocked1.equals("enabled")){
        //enable the button 
    }else{
        //disbale the button 
    }

Answer 3

嘗試此操作，如果您之前單擊過兩次活動，則下次運行該活動時，它將禁用按鈕；

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);

                }


            }
        }
    });
}