将上下文传递给 ListView 的自定义适配器

Question

我有一个名为 Contacts 的类，它接受来自另一个活动的数据并创建一个自定义 ListView。我的困境在于我的 CustomAdapter 类。我尝试将我的 Activity 上下文传递给我的 CustomAdapter 的构造函数。我试过了，使用 this、Contacts.this 并没有工作。我所有的小部件都没有使用适当的文本进行更新。所以我的自定义 ListView 将加载，但那里什么都没有。相反，我通过了 getApplicationContext()。这行得通，但我必须在我的自定义适配器类中设置标志，我不确定这是否是最佳编程实践。首先，这是我的联系人活动文件

public class Contacts extends AppCompatActivity implements View.OnClickListener {
private Button addContactBtn;
private ListView contactList;
private CustomAdapter customAdapter;
private ArrayList<String> names = new ArrayList<>();
private ArrayList<String> phoneNums = new ArrayList<>();
private ArrayList<String> emails = new ArrayList<>();
static final int REQUEST_CODE = 1;



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

    addContactBtn = (Button)findViewById(R.id.contactAddButton);
    contactList = (ListView)findViewById(R.id.contactList);

    addContactBtn.setOnClickListener(this);

    customAdapter = new CustomAdapter(getApplicationContext(),names,phoneNums,emails);
    contactList.setAdapter(customAdapter);
}


@Override
public void onClick(View v) {
    switch (v.getId()){
        case R.id.contactAddButton:{
            Intent i = new Intent(Contacts.this, AddContact.class);
            startActivityForResult(i,REQUEST_CODE);

        }

    }
}

@Override
protected void onActivityResult(int requestCode, int resultCode, Intent data) {
    if(requestCode == REQUEST_CODE){
        if(resultCode == RESULT_OK){
            String name = data.getStringExtra("name");
            String phone = data.getStringExtra("phone");
            String email = data.getStringExtra("email");
            phoneNums.add(phone);
            names.add(name);
            emails.add(email);
        }
    }
}

}

接下来，这是我的 CustomAdapter 类。我在这里传递了我的上下文，这就是我遇到问题的地方。我为某些小部件设置了 onClick。我希望他们在单击时启动另一个意图，特别是打开 android 的拨号屏幕。一切都设置得很好，但是当我单击 CustomList 视图中的小部件时，应用程序崩溃了。我可以通过设置标志来解决这个问题，但我宁愿解决上下文问题。为什么我传递的上下文会导致此问题？我该如何解决？

public CustomAdapter(Context c,ArrayList<String>n, ArrayList<String>nums, ArrayList<String>e){

    context = c;
    phoneNumbers = nums;
    names = n;
    emails = e;
    inflater = (LayoutInflater)context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);

}
@Override
public int getCount() {
    return phoneNumbers.size();
}

@Override
public Object getItem(int position) {
    return position;
}

@Override
public long getItemId(int position) {
    return (long)position;
}

@Override
public View getView(int position, View convertView, ViewGroup parent) {
    View view = convertView;

    if (view == null){
        view = inflater.inflate(R.layout.contacts_custom_row,null);
        TextView name = (TextView)view.findViewById(R.id.customRowContactName);
        TextView phone = (TextView)view.findViewById(R.id.customRowContactNumber);
        TextView email = (TextView)view.findViewById(R.id.customRowContactEmail);

        name.setText(names.get(position));
        phone.setText(phoneNumbers.get(position));
        email.setText(emails.get(position));

        phone.setOnClickListener(this);
    }
    return view;
}

@Override
public void onClick(View v) {
    switch (v.getId()){
        case R.id.customRowContactNumber:{
            Intent i = new Intent(Intent.ACTION_DIAL);
            context.startActivity(i);//THIS IS THE ISSUE I THINK
            break;
        }
    }

}

这是 Log Cat 错误：

09-22 10:38:25.679    2794-2794/com.markfeldman.mydoggydays E/AndroidRuntime﹕ FATAL EXCEPTION: main
Process: com.markfeldman.mydoggydays, PID: 2794
android.util.AndroidRuntimeException: Calling startActivity() from outside of an Activity  context requires the FLAG_ACTIVITY_NEW_TASK flag. Is this really what you want?
        at android.app.ContextImpl.startActivity(ContextImpl.java:1238)
        at android.app.ContextImpl.startActivity(ContextImpl.java:1225)
        at android.content.ContextWrapper.startActivity(ContextWrapper.java:323)
        at com.markfeldman.mydoggydays.CustomAdapter.onClick(CustomAdapter.java:73)
        at android.view.View.performClick(View.java:4780)
        at android.view.View$PerformClick.run(View.java:19866)
        at android.os.Handler.handleCallback(Handler.java:739)
        at android.os.Handler.dispatchMessage(Handler.java:95)
        at android.os.Looper.loop(Looper.java:135)
        at android.app.ActivityThread.main(ActivityThread.java:5257)
        at java.lang.reflect.Method.invoke(Native Method)
        at java.lang.reflect.Method.invoke(Method.java:372)
        at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:903)
        at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:698)

Answer 1

您正在使用Context 调用另一个活动，因此它认为您正在尝试在活动外部调用，因此您需要使用标志FLAG_ACTIVITY_NEW_TASK。 相反，您可以尝试传递Activity。像下面这样：

public CustomAdapter(Contacts activity,ArrayList<String>n, ArrayList<String>nums, ArrayList<String>e){

    mActivity = activity;
    phoneNumbers = nums;
    names = n;
    emails = e;
    inflater = (LayoutInflater)context.getSystemService(Context.LAYOUT_INFLATER_SERVICE);

}

@Override
public void onClick(View v) {
    switch (v.getId()){
        case R.id.customRowContactNumber:{
            Intent i = new Intent(Intent.ACTION_DIAL);
            mActivity.startActivity(i);//THIS IS THE ISSUE I THINK
            break;
        }
    }

}

然后你可以像这样调用：

customAdapter = new CustomAdapter(Contacts.this,names,phoneNums,emails);
contactList.setAdapter(customAdapter);