如何让View高度随宽度自动调整？FrameLayout高度设为宽度70%

Hey there! Let's break down these two Android layout adaptation questions—they’re super common, so I’ll walk you through the most practical solutions for each.

There are a few reliable ways to achieve this, depending on your layout setup:

• Use ConstraintLayout's dimension ratio constraint (most straightforward)
  Wrap your target View in a ConstraintLayout, set its width/height to 0dp (match_constraint), then use app:layout_constraintDimensionRatio to define the width-to-height ratio. For example:

  <androidx.constraintlayout.widget.ConstraintLayout
      android:layout_width="match_parent"
      android:layout_height="wrap_content">
  
      <View
          android:id="@+id/adaptive_view"
          android:layout_width="match_parent"
          android:layout_height="0dp"
          app:layout_constraintDimensionRatio="H,1:1" <!-- H = height based on width; 1:1 means square -->
          app:layout_constraintTop_toTopOf="parent"
          app:layout_constraintStart_toStartOf="parent"/>
  </androidx.constraintlayout.widget.ConstraintLayout>
  

  Note: Use H to base height on width, or W to base width on height. Adjust the ratio (e.g., 2:1 for height = 50% of width) as needed.

• Custom View with overridden onMeasure
  If you can’t use ConstraintLayout, create a custom View that calculates its height manually in onMeasure:

  public class AdaptiveHeightView extends View {
      private float widthToHeightRatio = 1.0f; // Default 1:1
  
      public AdaptiveHeightView(Context context) {
          super(context);
      }
  
      public AdaptiveHeightView(Context context, AttributeSet attrs) {
          super(context, attrs);
          // Optional: Add custom attributes to set the ratio via XML
          TypedArray ta = context.obtainStyledAttributes(attrs, R.styleable.AdaptiveHeightView);
          widthToHeightRatio = ta.getFloat(R.styleable.AdaptiveHeightView_ratio, 1.0f);
          ta.recycle();
      }
  
      @Override
      protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
          int measuredWidth = MeasureSpec.getSize(widthMeasureSpec);
          int calculatedHeight = (int) (measuredWidth * widthToHeightRatio);
          setMeasuredDimension(measuredWidth, calculatedHeight);
      }
  }
  

  Then use this custom View in your layout—its height will automatically match the width based on your set ratio.

• Use AndroidX's AspectRatioFrameLayout
  Google’s AndroidX library provides a dedicated layout for this use case:

  <androidx.aspectratio.widget.AspectRatioFrameLayout
      android:layout_width="match_parent"
      android:layout_height="wrap_content"
      app:aspectRatio="1.77" <!-- 16:9 ratio, for example -->
      app:aspectRatioEnabled="true">
  
      <!-- Your child View goes here -->
      <FrameLayout
          android:layout_width="match_parent"
          android:layout_height="match_parent"/>
  
  </androidx.aspectratio.widget.AspectRatioFrameLayout>
  

Given your existing FrameLayout (width set to match_parent), here’s how to make its height 70% of its width:

Option 1: Use ConstraintLayout (simplest approach) #

Wrap your FrameLayout in a ConstraintLayout, adjust its height to 0dp, and set the dimension ratio to 10:7 (since 7/10 = 70%):

<androidx.constraintlayout.widget.ConstraintLayout
    android:layout_width="match_parent"
    android:layout_height="wrap_content">

    <FrameLayout
        android:id="@+id/fiew"
        android:layout_width="match_parent"
        android:layout_height="0dp"
        android:layout_marginLeft="20dp"
        android:layout_marginRight="20dp"
        android:layout_marginTop="20dp"
        app:layout_constraintDimensionRatio="H,10:7" <!-- Height = 70% of width -->
        app:layout_constraintTop_toTopOf="parent"
        app:layout_constraintStart_toStartOf="parent"/>

</androidx.constraintlayout.widget.ConstraintLayout>

Option 2: Custom FrameLayout #

If you prefer not to use ConstraintLayout, create a custom FrameLayout that overrides onMeasure:

public class RatioFrameLayout extends FrameLayout {
    private final float heightToWidthRatio = 0.7f; // 70%

    public RatioFrameLayout(Context context) {
        super(context);
    }

    public RatioFrameLayout(Context context, AttributeSet attrs) {
        super(context, attrs);
    }

    @Override
    protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
        int measuredWidth = MeasureSpec.getSize(widthMeasureSpec);
        int calculatedHeight = (int) (measuredWidth * heightToWidthRatio);
        // Update height measure spec to our calculated value
        heightMeasureSpec = MeasureSpec.makeMeasureSpec(calculatedHeight, MeasureSpec.EXACTLY);
        super.onMeasure(widthMeasureSpec, heightMeasureSpec);
    }
}

Then replace your original FrameLayout with this custom one in XML:

<com.yourpackage.RatioFrameLayout
    android:id="@+id/fiew"
    android:layout_width="match_parent"
    android:layout_height="wrap_content" <!-- This will be overridden by onMeasure -->
    android:layout_marginLeft="20dp"
    android:layout_marginRight="20dp"
    android:layout_marginTop="20dp">

</com.yourpackage.RatioFrameLayout>

内容的提问来源于stack exchange，提问作者D T