Android FLAG_ACTIVITY_NEW_TASK无法正常工作

Question

我在自定义的onClick监听器中调用startActivity（）方法时遇到了问题。代码编译得很好，但是当它到达执行的那一点时，我得到一个nullPointerException。

代码

private static class ProverbAdapter extends ArrayAdapter<String> { 
    MainActivity ma; 
    public ProverbAdapter(Context context, int layout, int resId, String[] items) { 
     super(context, layout, resId, items); 
     this.ma = new MainActivity(); 
    } 

    @Override 
    public View getView(int position, View convertView, ViewGroup parent) { 
     View row = convertView; 
     Context context = getContext(); 
     if(row == null) { 
      row = LayoutInflater.from(context).inflate(R.layout.proverb_layout, parent, false); 
     } 

     String item = getItem(position); 
     TextView proverbDate = (TextView)row.findViewById(R.id.proverb_date); 
     TextView proverbText = (TextView)row.findViewById(R.id.proverb_content); 
     String[] data = item.split("----"); 
     proverbDate.setText(data[0]); 
     proverbText.setText(data[1]); 

     ImageButton emailButton = (ImageButton)row.findViewById(R.id.emailButton); 
     ImageButton twitterButton = (ImageButton)row.findViewById(R.id.twitterButton); 
     ImageButton facebookButton = (ImageButton)row.findViewById(R.id.facebookButton); 

     emailButton.setOnClickListener(this.ma.new ProverbOnClickListener(data[0], data[1], "email", context)); 
     twitterButton.setOnClickListener(this.ma.new ProverbOnClickListener(data[0], data[1], "twitter", context)); 
     facebookButton.setOnClickListener(this.ma.new ProverbOnClickListener(data[0], data[1], "facebook", context)); 

     return row; 
    } 
} 

public class ProverbOnClickListener implements OnClickListener { 

    String proverb_date, proverb_content, eventType; 
    Context context; 

    public ProverbOnClickListener(String proverb_date, String proverb_content, String eventType, Context context) { 
      this.proverb_date = proverb_date; 
      this.proverb_content = proverb_content; 
      this.eventType = eventType; 
      this.context = context; 
    } 

    @Override 
    public void onClick(View v) { 
     Toast.makeText(this.context, this.eventType + ": " + this.proverb_content, Toast.LENGTH_SHORT).show(); 
     if(this.eventType == "email") { 
      Intent i = new Intent(Intent.ACTION_SEND); 
        i.addFlags(Intent.FLAG_ACTIVITY_NEW_TASK); 
      i.setType("message/rfc822"); 
      i.putExtra(Intent.EXTRA_EMAIL , new String[]{"recipient@example.com"}); 
      i.putExtra(Intent.EXTRA_SUBJECT, "subject of email"); 
      i.putExtra(Intent.EXTRA_TEXT , "body of email"); 
      try { 
       context.startActivity(Intent.createChooser(i, "Send mail...")); 
      } catch (android.content.ActivityNotFoundException ex) { 
       Toast.makeText(this.context, "There are no email clients installed.", Toast.LENGTH_SHORT).show(); 
      } 
     } 
    } 

    } 

异常

致命异常：主android.util.AndroidRuntimeException：从一个活动上下文之外调用startActivity（）需要FLAG_ACTIVITY_NEW_TASK标志。这真的是你想要的吗？

我添加了新的标志作为编译器建议，但它仍然崩溃与相同的错误。

* 编辑 * ***

第一响应以下建议后，我的适配器现在的样子：

private static class ProverbAdapter extends ArrayAdapter<String> { 
    Context context; 
    public ProverbAdapter(Context context, int layout, int resId, String[] items) { 
     super(context, layout, resId, items); 
     this.context = context; 
    } 

    @Override 
    public View getView(int position, View convertView, ViewGroup parent) { 
     View row = convertView; 
     if(row == null) { 
      LayoutInflater li = (LayoutInflater) context.getSystemService(Context.LAYOUT_INFLATER_SERVICE); 
      row = li.inflate(R.layout.proverb_layout, parent, false); 
     } 

     String item = getItem(position); 
     TextView proverbDate = (TextView)row.findViewById(R.id.proverb_date); 
     TextView proverbText = (TextView)row.findViewById(R.id.proverb_content); 
     String[] data = item.split("----"); 
     proverbDate.setText(data[0]); 
     proverbText.setText(data[1]); 

     ImageButton emailButton = (ImageButton)row.findViewById(R.id.emailButton); 
     ImageButton twitterButton = (ImageButton)row.findViewById(R.id.twitterButton); 
     ImageButton facebookButton = (ImageButton)row.findViewById(R.id.facebookButton); 

     emailButton.setOnClickListener(new ProverbOnClickListener(data[0], data[1], "email", context)); 
     twitterButton.setOnClickListener(new ProverbOnClickListener(data[0], data[1], "twitter", context)); 
     facebookButton.setOnClickListener(new ProverbOnClickListener(data[0], data[1], "facebook", context)); 

     return row; 
    } 
} 

但是我收到一个编译错误。

没有可以访问MainActivity的封闭实例类型。

Answer 1

尝试一些修改

this.ma = new MainActivity(); //it is wrong 

不要实例化活动

尝试这样

Context context; 
    public ProverbAdapter(Context context, int layout, int resId, String[] items) { 
     super(context, layout, resId, items); 
     this.context=context; 
    } 

使用这个变量情况下在任何你需要的上下文