Question

enter image description here我在activity_main.xml的设计标签中添加了两个滑块和两个textview，当我运行应用时，它们似乎不会出现。我没有收到任何错误，所以我很困惑可能导致小部件在运行时不出现在应用程序中的原因。还有其他人经历过吗？如果是这样，这个问题是如何解决的？提前谢谢。

   <?xml version="1.0" encoding="utf-8"?>
<android.support.constraint.ConstraintLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:app="http://schemas.android.com/apk/res-auto"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context="com.example.umeer.drawindapp1.MainActivity">


<Button
    android:id="@+id/button"
    android:layout_width="wrap_content"
    android:layout_height="40dp"
    android:layout_marginBottom="8dp"
    android:layout_marginEnd="8dp"
    android:layout_marginStart="8dp"
    android:layout_marginTop="8dp"
    android:hint="@string/clear"
    app:layout_constraintBottom_toBottomOf="parent"
    app:layout_constraintEnd_toEndOf="parent"
    app:layout_constraintHorizontal_bias="0.973"
    app:layout_constraintStart_toStartOf="parent"
    app:layout_constraintTop_toTopOf="parent"
    app:layout_constraintVertical_bias="0.014" />

<TextView
    android:id="@+id/textView"
    android:layout_width="60dp"
    android:layout_height="18dp"
    android:layout_marginBottom="8dp"
    android:layout_marginStart="8dp"
    android:layout_marginTop="8dp"
    android:hint="@string/width"
    app:layout_constraintBottom_toTopOf="@+id/textView2"
    app:layout_constraintStart_toStartOf="parent"
    app:layout_constraintTop_toTopOf="parent"
    app:layout_constraintVertical_bias="1.0" />

<TextView
    android:id="@+id/textView2"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_marginBottom="8dp"
    android:layout_marginStart="8dp"
    android:hint="@string/opacity"
    app:layout_constraintBottom_toBottomOf="parent"
    app:layout_constraintStart_toStartOf="parent" />

<SeekBar
    android:id="@+id/seekBar2"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_marginBottom="8dp"
    android:layout_marginEnd="8dp"
    android:layout_marginStart="8dp"
    app:layout_constraintBottom_toBottomOf="parent"
    app:layout_constraintEnd_toEndOf="parent"
    app:layout_constraintStart_toEndOf="@+id/textView2" />

<SeekBar
    android:id="@+id/seekBar3"
    android:layout_width="wrap_content"
    android:layout_height="wrap_content"
    android:layout_marginBottom="8dp"
    android:layout_marginEnd="8dp"
    android:layout_marginStart="8dp"
    android:layout_marginTop="8dp"
    app:layout_constraintBottom_toTopOf="@+id/seekBar2"
    app:layout_constraintEnd_toEndOf="parent"
    app:layout_constraintStart_toEndOf="@+id/textView"
    app:layout_constraintTop_toTopOf="parent"
    app:layout_constraintVertical_bias="0.996" />

</android.support.constraint.ConstraintLayout>

screenshot of the app and design tab

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.widget.Button;

public class MainActivity extends AppCompatActivity {

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);

        MyDraw d = new MyDraw(this);
        setContentView(d);

        Button b = findViewById(R.id.button);
    }

Mydraw是我正在使用的视图，但程序不允许我使用Button b = findViewByID（d.id.button）

Android Studio小部件不会出现在应用中

0 个答案: