src/android/src/com/google/android/inputmethod/japanese/ui/PopUpLayouter.java

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package org.mozc.android.inputmethod.japanese.ui;

import org.mozc.android.inputmethod.japanese.MozcUtil;
import com.google.common.base.Preconditions;

import android.graphics.Rect;
import android.view.Gravity;
import android.view.View;
import android.view.ViewGroup;
import android.view.ViewGroup.MarginLayoutParams;
import android.widget.FrameLayout;

/**
 * A pop-up view layouter.
 * <p>
 * This class registers given popup View as a direct child of root View.
 * This makes the popup be able to appear to anywhere in the screen.
 * To control the position a Bounds should be specified. It will be converted into a LayoutParams
 * internally.
 */
public class PopUpLayouter<T extends View> {

  private final View parent;
  private final T contentView;

  private boolean isRegistered = false;

  public PopUpLayouter(View parent, T popUpView) {
    this.parent = Preconditions.checkNotNull(parent);
    this.contentView = Preconditions.checkNotNull(popUpView);
  }

  private void registerToViewHierarchyIfNecessary() {
    if (isRegistered) {
      return;
    }

    View rootView = parent.getRootView();
    if (rootView != null) {
      FrameLayout screenContent =
          FrameLayout.class.cast(rootView.findViewById(android.R.id.content));
      if (screenContent != null) {
        screenContent.addView(
            contentView, new FrameLayout.LayoutParams(0, 0, Gravity.LEFT | Gravity.TOP));
        isRegistered = true;
      }
    }
  }

  public T getContentView() {
    return contentView;
  }

  public void setBounds(Rect rect) {
    Preconditions.checkNotNull(rect);
    setBounds(rect.left, rect.top, rect.right, rect.bottom);
  }

  public void setBounds(int left, int top, int right, int bottom) {
    registerToViewHierarchyIfNecessary();

    int width = right - left;
    int height = bottom - top;

    ViewGroup.LayoutParams layoutParams = contentView.getLayoutParams();
    if (layoutParams != null) {
      layoutParams.width = width;
      layoutParams.height = height;
      if (MarginLayoutParams.class.isInstance(layoutParams)) {
        int x = left;
        int y = top;

        int[] location = new int[2];
        parent.getLocationInWindow(location);
        x += location[0];
        y += location[1];

        MarginLayoutParams marginLayoutParams = MarginLayoutParams.class.cast(layoutParams);
        // Clip XY.
        View rootView = View.class.cast(contentView.getParent());
        if (rootView != null) {
          x = MozcUtil.clamp(x, 0, rootView.getWidth() - width);
          y = MozcUtil.clamp(y, 0, rootView.getHeight() - height);
        }

        marginLayoutParams.setMargins(x, y, 0, 0);
      }
      contentView.setLayoutParams(layoutParams);
    }
  }
}