Android GridLayout 子元素如何平均分配螢幕寬度？程式碼動態設定 LayoutParams 實現

問題

XML 中 GridLayout 設定 layout_columnWeight/layout_rowWeight 在 API 21+ 才支援，且行為不穩定。計算機鍵盤等等寬佈局需求無法靠 XML 靜態屬性解決。

解決方案：Java/Kotlin 動態計算並套用 LayoutParams

// 工具類：取得螢幕寬度
public class ScreenUtils {
    public static int getScreenWidth(Context context) {
        WindowManager wm = (WindowManager) context.getSystemService(Context.WINDOW_SERVICE);
        DisplayMetrics dm = new DisplayMetrics();
        wm.getDefaultDisplay().getMetrics(dm);
        return dm.widthPixels;
    }
}

// Activity/Fragment 中動態加載 GridLayout 子視圖
final int COL_COUNT = 4; // 計算機 4 列
GridLayout grid = findViewById(R.id.gridLayout);
grid.setColumnCount(COL_COUNT);
grid.setRowCount(5); // 視按鈕行數

for (int i = 0; i < buttonLabels.length; i++) {
    View btn = LayoutInflater.from(this).inflate(R.layout.btn_key, grid, false);
    ((TextView) btn.findViewById(R.id.tv_label)).setText(buttonLabels[i]);
    
    // 關鍵：寬度 = 螢幕寬度 / 列數，高度包裹內容
    GridLayout.LayoutParams lp = new GridLayout.LayoutParams();
    lp.width = ScreenUtils.getScreenWidth(this) / COL_COUNT;
    lp.height = GridLayout.LayoutParams.WRAP_CONTENT;
    lp.setGravity(Gravity.FILL_HORIZONTAL);
    lp.columnSpec = GridLayout.spec(GridLayout.UNDEFINED, 1f); // 權重 1
    lp.rowSpec = GridLayout.spec(GridLayout.UNDEFINED, 1f);
    btn.setLayoutParams(lp);
    
    grid.addView(btn);
}

關鍵點解析

• lp.width = screenWidth / COL_COUNT：強制像素寬度，繞過權重機制不可靠問題。
• lp.columnSpec/rowSpec = spec(UNDEFINED, 1f)：仍宣告權重 1，配合固定寬度雙重保障。
• Gravity.FILL_HORIZONTAL：子視圖內部內容水平置中/填滿。
• 若需間距，改用 GridLayout.LayoutParams.setMargins() 並相應減少 lp.width。

Kotlin 簡潔版

val colCount = 4
val btnWidth = resources.displayMetrics.widthPixels / colCount
gridLayout.columnCount = colCount
buttonLabels.forEachIndexed { idx, label ->
    val btn = layoutInflater.inflate(R.layout.btn_key, gridLayout, false).apply {
        findViewById(R.id.tv_label).text = label
        layoutParams = GridLayout.LayoutParams().apply {
            width = btnWidth
            height = GridLayout.LayoutParams.WRAP_CONTENT
            setGravity(Gravity.FILL_HORIZONTAL)
            columnSpec = GridLayout.spec(GridLayout.UNDEFINED, 1f)
            rowSpec = GridLayout.spec(GridLayout.UNDEFINED, 1f)
        }
    }
    gridLayout.addView(btn)
}

替代方案：ConstraintLayout + Guideline/鏈

現代佈局首選 ConstraintLayout，用 Guideline 等分螢幕，再建立水平鏈，XML 即可完成等寬佈局，效能優於巢狀 GridLayout/LinearLayout。