如何进行一次操作调用

Question

假设我有无限的 viewpager 并且每个都被着色了。所以在关闭应用程序时再次调用该操作，但我想要的是下次启动时不应再次调用该操作

Answer 1

您应该在该操作后使用 SharedPreferences 存储一个布尔值 "firstTime"。在循环之前恢复该值并更改图像数组。

Answer 2

这是您设置共享首选项的方式：

    SharedPreferences preferences = context.getSharedPreferences("my_prefs", Context.MODE_PRIVATE);
    SharedPreferences.Editor editor = preferences.edit();
    editor.putInt("page" + mCurrentPage, randInt);
    editor.commit();

要检索它们，您需要执行以下操作：

    int randInt = preferences.getInt("page" + mCurrentPage, -1);

代码：

    SharedPreferences preferences = getActivity().getSharedPreferences("my_prefs", Context.MODE_PRIVATE);
    int randInt = preferences.getInt("page" + mCurrentPage, -1);
    if(randInt == -1) {
        randInt = new Random().nextInt((8));
        SharedPreferences.Editor editor = preferences.edit();
        editor.putInt("page" + mCurrentPage, randInt);
        editor.commit();
    }

Answer 3

根据您的问题、此讨论和 project link，只需尝试一下：

在MainActivity中添加这两个全局变量：

/**
 * {@link SharedPreferences} key for the random int array.
 */
public static final String KEY_RANDOM_INT_FOR_INDEX = "random_int_index";

/**
 * Value holding the total number of images.
 */
public static final int TOTAL_IMAGES = 8;

然后在MainActivity的onCreate的末尾再次添加：

// Get a reference to the default SharedPreferences
SharedPreferences defSharedPreference = PreferenceManager
        .getDefaultSharedPreferences(this);
// Check if there is a random int for at least 1 index
if (defSharedPreference.getInt(KEY_RANDOM_INT_FOR_INDEX + "_0", -1) == -1) {
    // Generate array of <TOTAL_IMAGES> random ints;
    ArrayList<Integer> allInts = new ArrayList<Integer>();
    for (int i = 0; i < TOTAL_IMAGES; i++) {
        allInts.add(i);
    }
    // Editor instance for modifying SharedPreferences;
    SharedPreferences.Editor sp_editor = defSharedPreference.edit();
    // Generate random ints;
    for (int i = 0; i < TOTAL_IMAGES; i++) {
        int range = allInts.size();
        int pickIndex = (int) (Math.random() * range);
        int value = allInts.remove(pickIndex);
        // System.out.print("\nindex: " + i + "\t=\t" + value);
        // Save the random value with the key;
        sp_editor.putInt(KEY_RANDOM_INT_FOR_INDEX + "_" + i, value);
    }
    // Save the editors queue in the SharedPreferences;
    sp_editor.commit();
}

最后在 MyFragment 的 onCreateView 中添加：

// Get a reference to the default SharedPreferences
SharedPreferences defSharedPreference = PreferenceManager
        .getDefaultSharedPreferences(getActivity());
// Calculate the index of the page from base of TOTAL_IMAGES;
int pageIndexInTotalImages = (mCurrentPage - 1)
        % MainActivity.TOTAL_IMAGES;
// Calculate the index of the random image for the page;
int imageID = defSharedPreference.getInt(
        MainActivity.KEY_RANDOM_INT_FOR_INDEX + "_"
                + pageIndexInTotalImages, 0);
int resourceImageID = imageID + R.drawable.image0;

假设您在 myfragment_layout 中设置了 ImageView，您可以使用以下方式加载图像：

<ImageView>.setImageResource(resourceImageID);

如何进行一次操作调用

How to make an operation calls once

android

android-fragments

android-viewpager