ConstraintLayout 无法转换为 android.widget.TextView

Question

当我尝试启动 activity.

时，我不断收到运行时错误

发生错误的行：

private OnItemClickListener mDeviceClickListener = new OnItemClickListener() {
    public void onItemClick(AdapterView<?> av, View v, int arg2, long arg3) {

        textView1.setText("Csatlakozás...");
        String info = ((TextView) v).getText().toString(); // <-- ERROR HERE
        String address = info.substring(info.length() - 17);
        Intent i = new Intent(DeviceListActivity.this, MainActivity.class);
        i.putExtra(EXTRA_DEVICE_ADDRESS, address);
        startActivity(i);
    }
};

Logcat:

java.lang.ClassCastException: android.support.constraint.ConstraintLayout cannot be cast to android.widget.TextView at arduinosensors.example.com.smarthome3.DeviceListActivity.onItemClick(DeviceListActivity.java:106)

这里发生了什么？在我开始使用具有自定义行布局的自定义数组适配器之前一切都很好。

编辑：

custom_row.xml

<?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout
    xmlns:android="http://schemas.android.com/apk/res/android" android:layout_width="match_parent"
    android:layout_height="match_parent">

    <LinearLayout
        android:layout_width="match_parent"
        android:layout_height="match_parent"
        android:orientation="horizontal">

        <TextView
            android:id="@+id/textView"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:text="TextView"
            android:textSize="18sp"
            android:textStyle="bold" />

        <TextView
            android:id="@+id/textView2"
            android:layout_width="wrap_content"
            android:layout_height="wrap_content"
            android:layout_weight="1"
            android:text="TextView"
            android:textSize="18sp" />
    </LinearLayout>

</android.support.constraint.ConstraintLayout>

我的适配器：

public class UsersAdapter extends ArrayAdapter<Adapter> {
    public UsersAdapter(Context context, ArrayList<Adapter> users) {
        super(context, 0, users);
    }

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

        Adapter user = getItem(position);

        if (convertView == null) {
            LayoutInflater sontInflater = LayoutInflater.from(getContext());
            convertView = sontInflater.inflate(R.layout.custom_row,parent,false);
        }

        TextView one = (TextView) convertView.findViewById(R.id.textView);
        TextView two = (TextView) convertView.findViewById(R.id.textView2);

        one.setText(user.name);
        two.setText(user.hometown);

        return convertView;
    }
}

Answer 1

来自documentation：

View: The view within the AdapterView that was clicked (this will be a view provided by the adapter)

在你的例子中 View 是根 ConstraintLayout。正如错误所说，您不能将其转换为 TextView。要获取信息，您可以使用：

String info = v.findViewById(R.id.textView).getText().toString()

Answer 2

你刚刚为你的约束布局弄错了 id，并将它与你在 MainActivity 中声明的 textview 混淆了

ConstraintLayout 无法转换为 android.widget.TextView

ConstraintLayout cannot be cast to android.widget.TextView

java

android

casting

adapter