Question

我正在android studio中制作该应用程序，在我的应用程序中添加了该功能，如果用户第二次单击按钮，则该按钮被禁用并以共享优先级保存按钮的状态，并且如果用户关闭了该应用程序，再次打开应用程序，然后显示保存按钮状态（如果禁用了按钮，则显示禁用按钮，否则显示启用状态）。我在代码中放入了许多共享偏好代码，但是每次出现空对象引用时。我的代码在下面给出，我将共享的首选项代码放在此按钮上，但是如何？

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);

                    }


                }
            }

        });

Answer 1

请参考下面的代码。并且请记住，您可以使用首选项名称（"MY_PREF"）和密钥名称（"DOWNLOAD_BUTTON_STATUS"）来更改应用程序中其他位置的首选项。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);
}

Answer 2

///单击按钮添加此代码

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

///在OnCreate / OncreateView方法中添加此代码

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

Answer 3

尝试此操作，如果您之前单击过两次活动，则下次运行该活动时将禁用该按钮；

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);

                }


            }
        }
    });
}

保存按钮状态（启用和禁用）

3 个答案: