Android 简单实现一个流式布局的示例

Z时代
2024-01-10
分类：综合

本篇文章主要介绍了Android 简单实现一个流式布局的示例，分享给大家，具体如下：

流式布局应该是我们很常见的一种布局了，在很多场景下都会遇到它，例如：标签之类的功能等。用轮子不如造轮子来的爽，这里自己简单的实现下流式布局：

onMeasure

onLayout

通过以上两个方法我们就可以完成对流式布局的基本操作：

onMeasure


  @Override
  protected void onMeasure(int widthMeasureSpec, int heightMeasureSpec) {
    super.onMeasure(widthMeasureSpec, heightMeasureSpec);
    // 获得它的父容器为它设置的测量模式和大小
    int sizeWidth = MeasureSpec.getSize(widthMeasureSpec);
    int sizeHeight = MeasureSpec.getSize(heightMeasureSpec);
    int modeWidth = MeasureSpec.getMode(widthMeasureSpec);
    int modeHeight = MeasureSpec.getMode(heightMeasureSpec);
    // 如果是warp_content情况下，记录宽和高
    int width = 0;
    int height = 0;
    //记录每一行的宽度，width不断取最大宽度
    int lineWidth = 0;
    //记录每一行的宽度，不断累加每行最大高度获取height
    int lineHeight = 0;
    //获取子View的数量
    int childCount = getChildCount();
    //遍历每个子元素
    for (int i = 0; i < childCount; i++) {
      //获取每一个子View
      View childView = getChildAt(i);
      //测量每一个子View的宽和高
      measureChild(childView,widthMeasureSpec,heightMeasureSpec);
      //得到子View的lp
      LayoutParam lp = (LayoutParam) childView.getLayoutParams();
      //当前子View实际占据的宽度
      int childWidth = childView.getMeasuredWidth() + lp.leftMargin + lp.rightMargin;
      //当前子View实际占据的高度
      int childHeight = childView.getMeasuredHeight() + lp.bottomMargin + lp.topMargin;
      //如果加入当前childView，超出最大宽度，则得到目前最大宽度给width，类加height 然后开启新行
      if (lineWidth + childWidth > sizeWidth) {
        // 取最大的宽度
        width = Math.max(lineWidth, childWidth);
        //重新开启新行，重新计算
        lineWidth = childWidth;
        //叠加当前高度
        height += childHeight;
        //记录下一行高度
        lineHeight = childHeight;
      }else {
        // 累加值lineWidth,lineHeight取最大高度
        lineWidth += childWidth;
        lineHeight = Math.max(lineHeight,childHeight);
      }
      // 如果是最后一个，则将当前记录的最大宽度和当前lineWidth做比较
      if (i == childCount - 1) {
        width = Math.max(width,lineWidth);
        height += lineHeight;
      }
    }
    setMeasuredDimension(modeWidth == MeasureSpec.EXACTLY?sizeWidth:width,modeHeight == MeasureSpec.EXACTLY?sizeHeight:height);
  }

在onMeasure方法中负责设置子控件的测量模式和大小根据所有子控件设置自己的宽和高，一旦宽度超出最大宽度便进行换行处理。高度不断累加从而获取最终高度。

onLayout


  //存储所有的View，按行记录
  private List<List<View>> mAllViews = new ArrayList<>();
  //记录每一行的最大高度
  private List<Integer> mLineHeight = new ArrayList<>();
  @Override
  protected void onLayout(boolean changed, int l, int t, int r, int b) {
    mAllViews.clear();
    mLineHeight.clear();
    int lineWidth = 0;
    int lineHeight = 0;
    int width = getWidth();
    int childCount = getChildCount();
    // 存储每一行所有的childView
    List<View> lineViews = new ArrayList<>();
    for (int i = 0; i < childCount; i++) {
      View childView = getChildAt(i);
      LayoutParam lp = (LayoutParam) childView.getLayoutParams();
      int childWidth = childView.getMeasuredWidth() + lp.rightMargin + lp.leftMargin;
      int childHeight = childView.getMeasuredHeight() + lp.topMargin + lp.bottomMargin;
      if (lineWidth + childWidth > width) {
        // 记录这一行所有的View以及最大高度
        mLineHeight.add(lineHeight);
        // 将当前行的childView保存，然后开启新的ArrayList保存下一行的childView
        mAllViews.add(lineViews);
        lineWidth = 0;
        lineViews = new ArrayList<>();
      }
      //如果不需要换行，则累加
      lineWidth += childWidth;
      lineHeight = Math.max(lineHeight,childHeight);
      lineViews.add(childView);
    }
    // 记录最后一行
    mAllViews.add(lineViews);
    mLineHeight.add(lineHeight);
    int left = 0;
    int top = 0;
    // 得到总行数
    int size = mAllViews.size();
    for (int i = 0; i < size; i++) {
      // 每一行的所有的views
      lineViews = mAllViews.get(i);
      // 当前行的最大高度
      lineHeight = mLineHeight.get(i);
      for (View view : lineViews) {
        LayoutParam lp = (LayoutParam) view.getLayoutParams();
        //计算childView的left,top,right,bottom
        int lc = left + lp.leftMargin;
        int tc = top + lp.topMargin;
        int rc = lc + view.getMeasuredWidth();
        int bc = tc + view.getMeasuredHeight();
        view.layout(lc,tc,rc,bc);
        left += view.getMeasuredWidth() + lp.leftMargin + lp.rightMargin;
      }
      left = 0;
      top += lineHeight;
    }
  }

通过onLayout方法给子View布局，前提，我们必须得知道每个子View的宽度和高度。所以我们先要在onMeasure的时候，测量一下每个子View的具体大小。

测试


public class MainActivity extends AppCompatActivity {
  @Override
  protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);
    FlowLayout flowLayout = ((FlowLayout) findViewById(R.id.flowLayout));
    FlowLayout.LayoutParam params = new    FlowLayout.LayoutParam(ViewGroup.LayoutParams.WRAP_CONTENT, ViewGroup.LayoutParams.WRAP_CONTENT);
    params.setMargins(10,10,10,10);
    for (int i = 0; i < 10; i++) {
      TextView textView = new TextView(this);
      textView.setPadding(i * 10,10,i * 10,10);
      textView.setBackgroundColor(Color.BLUE);
      textView.setText("哈哈哈哈");
      textView.setTextColor(Color.WHITE);
      textView.setLayoutParams(params);
      flowLayout.addView(textView);
    }
  }
}

这里我们要注意下FlowLayout.LayoutParam params = new FlowLayout.LayoutParam(ViewGroup.LayoutParams.WRAP_CONTENT, ViewGroup.LayoutParams.WRAP_CONTENT);这个方法，有的小伙伴在写的过程中可能点不出来这个方法，那是因为这个方法是需要我们自己写一个静态内部类来实现。


@Override
  protected LayoutParams generateDefaultLayoutParams() {
    return new LayoutParam(LayoutParams.WRAP_CONTENT,LayoutParams.WRAP_CONTENT);
  }
  @Override
  public LayoutParams generateLayoutParams(AttributeSet attrs) {
    return new LayoutParam(getContext(),attrs);
  }
  @Override
  protected LayoutParams generateLayoutParams(LayoutParams p) {
    return new LayoutParam(p);
  }
  public static class LayoutParam extends MarginLayoutParams{
    public LayoutParam(Context c, AttributeSet attrs) {
      super(c, attrs);
    }
    public LayoutParam(@Px int width, @Px int height) {
      super(width, height);
    }
    public LayoutParam(MarginLayoutParams source) {
      super(source);
    }
    public LayoutParam(LayoutParams source) {
      super(source);
    }
  }