无法从 OnClickListener 启动 Activity “方法 startActivity(Intent, int) 未定义类型”

Question

我正在使用从 SQLite 数据库检索的项目填充 Scrollview，并使用下面的代码为每一行动态生成 OnClickListener。我希望 OnClickListener 中的代码将控制权返回给使用 Intent 调用它的 Activity（MealActivity），并传回被点击的项目的 id。

我已尝试使用下面的第二个代码段进行此操作，但出现编译错误：“方法 startActivity(Intent, int) 未定义 OnClickListenerSelectPresetItem 类型”。

如何从我的 OnClickListener 调用原始 Activity？

public class SelectPresetItemActivity extends Activity {

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

        if (savedInstanceState == null) {
            getFragmentManager().beginTransaction()
                    .add(R.id.container, new PlaceholderFragment()).commit();
        }

        readRecords();
    }

    public void readRecords() {
        LinearLayout linearLayoutRecords = (LinearLayout) findViewById(R.id.linearLayoutRecords);
        linearLayoutRecords.removeAllViews();

        List<preset_item> preset_item = new TableControllerPresetItem(this).read();

        if (preset_item.size() > 0) {

            for (preset_item obj : preset_item) {

                long id = obj.id;
                String PresetDesc = obj.preset_desc;
                int PresetMinutes = obj.preset_minutes;

                String textViewContents = PresetDesc + " - "
                        + PresetMinutes + " minutes";

                TextView textViewItem = new TextView(this);
                textViewItem.setPadding(0, 10, 0, 10);
                textViewItem.setText(textViewContents);
                textViewItem.setTag(Long.toString(id));

                textViewItem.setOnClickListener(new OnClickListenerSelectPresetItem());

                linearLayoutRecords.addView(textViewItem);
            }

        }

        else {

            TextView locationItem = new TextView(this);
            locationItem.setPadding(8, 8, 8, 8);
            locationItem.setText("No records yet.");

            linearLayoutRecords.addView(locationItem);
        }
    }listener

The method startActivity(Intent, int) is undefined for the type OnClickListenerSelectPresetItem


    public class SelectPresetItemActivity extends Activity {

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

            if (savedInstanceState == null) {
                getFragmentManager().beginTransaction()
                        .add(R.id.container, new PlaceholderFragment()).commit();
            }

            readRecords();
        }

        public void readRecords() {
            LinearLayout linearLayoutRecords = (LinearLayout) findViewById(R.id.linearLayoutRecords);
            linearLayoutRecords.removeAllViews();

            List<preset_item> preset_item = new TableControllerPresetItem(this).read();

            if (preset_item.size() > 0) {

                for (preset_item obj : preset_item) {

                    long id = obj.id;
                    String PresetDesc = obj.preset_desc;
                    int PresetMinutes = obj.preset_minutes;

                    String textViewContents = PresetDesc + " - "
                            + PresetMinutes + " minutes";

                    TextView textViewItem = new TextView(this);
                    textViewItem.setPadding(0, 10, 0, 10);
                    textViewItem.setText(textViewContents);
                    textViewItem.setTag(Long.toString(id));

                    textViewItem.setOnClickListener(new OnClickListenerSelectPresetItem());

                    linearLayoutRecords.addView(textViewItem);
                }

            }

            else {

                TextView locationItem = new TextView(this);
                locationItem.setPadding(8, 8, 8, 8);
                locationItem.setText("No records yet.");

                linearLayoutRecords.addView(locationItem);
            }
        }

这是 OnCLickListener 代码：

public class OnClickListenerSelectPresetItem implements OnClickListener {
    public final static String EXTRA_MEAL_ID = "com.ian.mealtimer.MEAL_ID";

    @Override
    public void onClick(View view) {

        Long selectedMealId = Long.valueOf(view.getTag().toString());
        Intent myIntent = new Intent(view.getContext(),
                MealActivity.class);
        long mealId = -1;
        myIntent.putExtra(EXTRA_MEAL_ID, selectedMealId);
        startActivity(myIntent, 0);

    }
}

Answer 1

您应该使用： startActivity (Intent intent)

有一个不同的方法，它有一个整数参数： startActivityForResult (Intent intent, int requestCode)

上下文也可以启动一个活动，所以你必须获取上下文。您可以轻松地从您的视图中获取它：

@Override
public void onClick(View view) {

    Long selectedMealId = Long.valueOf(view.getTag().toString());
    Intent myIntent = new Intent(view.getContext(),
            MealActivity.class);
    long mealId = -1;
    myIntent.putExtra(EXTRA_MEAL_ID, selectedMealId);
    view.getContext().startActivity(myIntent);
}

You can read more about starting activities here.

Answer 2

startActivity 是 Context 类的一个方法。 OnClickListener 不知道应该在哪个上下文中调用它。将上下文作为参数传递给 OnClickListener 的构造函数并将其保存在里面： 在 OnClickListenerSelectPresetItem 类中：

private Context context;
public OnClickListenerSelectPresetItem(Context context){
   this.context=context;
}

然后在这个上下文中调用 startActivity

this.context.startActivity(myIntent, 0);

并通过传递活动来构造它们

textViewItem.setOnClickListener(new OnClickListenerSelectPresetItem(this));

Answer 3

如何将活动传递给 OnClickListenerSelectPresetItem 的构造函数 然后像下面这样使用它：

public class OnClickListenerSelectPresetItem implements OnClickListener {
    public final static String EXTRA_MEAL_ID = "com.ian.mealtimer.MEAL_ID";
private SelectPresetItemActivity selectPresetItemActivity;
    public OnClickListenerSelectPresetItem(SelectPresetItemActivity selectPresetItemActivity){
this.selectPresetItemActivity = selectPresetItemActivity;
     }
    @Override
    public void onClick(View view) {

        Long selectedMealId = Long.valueOf(view.getTag().toString());
        Intent myIntent = new Intent(view.getContext(),
                MealActivity.class);
        long mealId = -1;
        myIntent.putExtra(EXTRA_MEAL_ID, selectedMealId);
        selectPresetItemActivity.startActivity(myIntent, 0);

    }
}