android.content.res.Resources android.content.Context.getResources()' 在空对象引用上

Question

我正在尝试在我的 SlidingTabLayout 上显示图标，所以在我的适配器中，我创建了类似的东西，我在寻找教程的时候发现它我编辑了你将使用 getDrawable 的部分，因为它说它已弃用并应用我找到的解决方案

    @Override
public CharSequence getPageTitle(int position) {

    Drawable image = ResourcesCompat.getDrawable(mContext.getResources(), icons[position], null);
    image.setBounds(0, 0, 48, 48);
    SpannableString sb = new SpannableString(" ");
    ImageSpan imageSpan = new ImageSpan(image, ImageSpan.ALIGN_BOTTOM);
    sb.setSpan(imageSpan, 0, 1, Spannable.SPAN_EXCLUSIVE_EXCLUSIVE);
    return sb;
}

我还在我的适配器上声明了这一点，我已经检查了我是否真的把它放在我的可绘制对象上并且所有这些都在那里。

  private int[] icons = {
        R.drawable.tabone,
        R.drawable.tabtwo,
        R.drawable.tabthree,
        R.drawable.tapfour,
        R.drawable.tabfive
};

我不知道我做错了什么，但我总是有这个错误

Attempt to invoke virtual method 'android.content.res.Resources android.content.Context.getResources()' on a null object reference

即使我声明了一个变量来处理图像。谁能帮帮我，我的最低版本是 14，我的目标 sdk 是 22。提前谢谢你。

这是我的适配器代码

public class ViewPagerAdapter extends FragmentStatePagerAdapter {

CharSequence Titles[]; 
int NumbOfTabs;

Context mContext;

private int[] icons = {
        R.drawable.tabone,
        R.drawable.tabtwo,
        R.drawable.tabthree,
        R.drawable.tapfour,
        R.drawable.tabfive
};


public ViewPagerAdapter(FragmentManager fm,CharSequence mTitles[], int mNumbOfTabsumb, Context context) {
    super(fm);

    this.Titles = mTitles;
    this.NumbOfTabs = mNumbOfTabsumb;
    this.mContext = context;

}


@Override
public Fragment getItem(int position) {

    if(position == 0) // if the position is 0 we are returning the First tab
    {
        Tabone tab_one = new Tabone();
        return tab_one;
    }
    else if(position == 1)
    {
        Tabtwo tab_two = new Tabtwo();
        return tab_two;

    }else if(position == 2){
        Tabthree tab_three = new Tabthree();
        return tab_three;
    }else if(position == 3){
        Tabfour tab_four = new Tabfour();
        return tab_four;
    }else{
        Tabfive tab_five = new Tabfive();
        return tab_five;
    }

}


@Override
public CharSequence getPageTitle(int position) {

    Drawable image = ResourcesCompat.getDrawable(mContext.getResources(), icons[position], null);
    image.setBounds(0, 0, 48, 48);
    SpannableString sb = new SpannableString(" ");
    ImageSpan imageSpan = new ImageSpan(image, ImageSpan.ALIGN_BOTTOM);
    sb.setSpan(imageSpan, 0, 1, Spannable.SPAN_EXCLUSIVE_EXCLUSIVE);
    return sb;
}



// This method return the Number of tabs for the tabs Strip

@Override
public int getCount() {
    return NumbOfTabs;
}

}

这是我的 MainActivity

private ViewPager mPager;
private ViewPagerAdapter adapter;
private SlidingTabLayout mTabs;
private Context mContext;

 CharSequence Titles[] =   {"One", "Two", "Three", "Four", "Five"};

int Numboftabs = 5;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    adapter = new ViewPagerAdapter(getSupportFragmentManager(), Titles, Numboftabs, mContext);

    // Assigning ViewPager View and setting the adapter
    mPager = (ViewPager) findViewById(R.id.pager);
    mPager.setAdapter(adapter);

    // Assigning the Sliding Tab Layout View
    mTabs = (SlidingTabLayout) findViewById(R.id.tabs);
    mTabs.setDistributeEvenly(true); 


    // Setting the ViewPager For the SlidingTabsLayout
    mTabs.setSelectedIndicatorColors(getResources().getColor(R.color.tabsIndicator));
    mTabs.setViewPager(mPager);
}

Answer 1

看这里：

adapter = new ViewPagerAdapter(getSupportFragmentManager(), Titles, Numboftabs, mContext);

从这里mContext 去null。因为您没有在 onCreate 方法中为 mContext 变量分配任何引用。

改成：

adapter = new ViewPagerAdapter(getSupportFragmentManager(), Titles, Numboftabs, MainActivity.this);

或者你也可以试试这个：

在onCreate 方法内：

mContext = MainActivity.this;

adapter = new ViewPagerAdapter(getSupportFragmentManager(), Titles, Numboftabs, mContext);

使用ViewPagerAdapter这个代码：

public class ViewPagerAdapter extends FragmentStatePagerAdapter { 

CharSequence Titles[]; 
int NumbOfTabs;

private Activity mContext;

private int[] icons = {
        R.drawable.tabone,
        R.drawable.tabtwo,
        R.drawable.tabthree,
        R.drawable.tapfour,
        R.drawable.tabfive
}; 


public ViewPagerAdapter(FragmentManager fm,CharSequence mTitles[], int mNumbOfTabsumb, Activity context) {
    super(fm); 

    this.Titles = mTitles;
    this.NumbOfTabs = mNumbOfTabsumb;
    this.mContext = context;

} 


@Override 
public Fragment getItem(int position) {

    if(position == 0) // if the position is 0 we are returning the First tab
    { 
        Tabone tab_one = new Tabone();
        return tab_one;
    } 
    else if(position == 1)
    { 
        Tabtwo tab_two = new Tabtwo();
        return tab_two;

    }else if(position == 2){
        Tabthree tab_three = new Tabthree();
        return tab_three;
    }else if(position == 3){
        Tabfour tab_four = new Tabfour();
        return tab_map; 
    }else{ 
        Tabfive tab_five = new Tabfive();
        return tab_five;
    } 

} 


    @Override 
public CharSequence getPageTitle(int position) {
    Drawable image = mContext.getResources().getDrawable(icons[position]);
    image.setBounds(0, 0, 48, 48);
    SpannableString sb = new SpannableString(" ");
    ImageSpan imageSpan = new ImageSpan(image, ImageSpan.ALIGN_BOTTOM);
    sb.setSpan(imageSpan, 0, 1, Spannable.SPAN_EXCLUSIVE_EXCLUSIVE);
    return sb;
}





// This method return the Number of tabs for the tabs Strip 

@Override 
public int getCount() { 
    return NumbOfTabs;
}