Android 开发问题：View 的 getWidth、getHeight 方法返回的值都为 0

java 复制代码

ImageView ivTest = findViewById(R.id.iv_test);

int width = ivTest.getWidth();
int height = ivTest.getHeight();

Log.i(TAG, "width: " + width);
Log.i(TAG, "height: " + height);

复制代码

# 输出结果

width: 0
height: 0

在 Android 开发中，上述代码中，getWidth、getHeight 方法返回的值都为 0

问题原因

当一个 Activity 启动时，视图的创建和显示需要经过几个关键阶段：视图创建阶段 -> 测量阶段 -> 布局阶段 -> 绘制阶段
在 onCreate 或过早的阶段调用这些方法时，视图尚未完成测量和布局流程，因此坐标值尚未计算，默认返回 0

处理策略

使用 View.post 方法，确保视图已完成布局

java 复制代码

ImageView ivTest = findViewById(R.id.iv_test);

ivTest.post(() -> {
    int width = ivTest.getWidth();
    int height = ivTest.getHeight();

    Log.i(TAG, "width: " + width);
    Log.i(TAG, "height: " + height);
});

补充学习

在 onCreate 方法中，任何需要等待测量和布局阶段完成后才能确定的信息都无法获取，例如

尺寸相关方法：getWidth、getHeight、getMeasuredWidth、getMeasuredHeight

java 复制代码

ImageView ivTest = findViewById(R.id.iv_test);

int width = ivTest.getWidth();
int height = ivTest.getHeight();

int measuredWidth = ivTest.getMeasuredWidth();
int measuredHeight = ivTest.getMeasuredHeight();

Log.i(TAG, "width: " + width);
Log.i(TAG, "height: " + height);

Log.i(TAG, "measuredWidth: " + measuredWidth);
Log.i(TAG, "measuredHeight: " + measuredHeight);

复制代码

# 输出结果

width: 0
height: 0
measuredWidth: 0
measuredHeight: 0

java 复制代码

// 使用 View.post 方法处理后

ImageView ivTest = findViewById(R.id.iv_test);

ivTest.post(() -> {
    int width = ivTest.getWidth();
    int height = ivTest.getHeight();

    int measuredWidth = ivTest.getMeasuredWidth();
    int measuredHeight = ivTest.getMeasuredHeight();

    Log.i(TAG, "width: " + width);
    Log.i(TAG, "height: " + height);

    Log.i(TAG, "measuredWidth: " + measuredWidth);
    Log.i(TAG, "measuredHeight: " + measuredHeight);
});

复制代码

# 输出结果

width: 200
height: 200
measuredWidth: 200
measuredHeight: 200

相对位置相关方法：getLeft、getRight、getTop、getBottom、getX、getY

java 复制代码

ImageView ivTest = findViewById(R.id.iv_test);

int left = ivTest.getLeft();
int right = ivTest.getRight();
int top = ivTest.getTop();
int bottom = ivTest.getBottom();

float x = ivTest.getX();
float y = ivTest.getY();

Log.i(TAG, "left: " + left);
Log.i(TAG, "right: " + right);
Log.i(TAG, "top: " + top);
Log.i(TAG, "bottom: " + bottom);

Log.i(TAG, "x: " + x);
Log.i(TAG, "y: " + y);

复制代码

# 输出结果

left: 0
right: 0
top: 0
bottom: 0
x: 0.0
y: 0.0

java 复制代码

// 使用 View.post 方法处理后

ImageView ivTest = findViewById(R.id.iv_test);

ivTest.post(() -> {
    int left = ivTest.getLeft();
    int right = ivTest.getRight();
    int top = ivTest.getTop();
    int bottom = ivTest.getBottom();

    float x = ivTest.getX();
    float y = ivTest.getY();

    Log.i(TAG, "left: " + left);
    Log.i(TAG, "right: " + right);
    Log.i(TAG, "top: " + top);
    Log.i(TAG, "bottom: " + bottom);

    Log.i(TAG, "x: " + x);
    Log.i(TAG, "y: " + y);
});

复制代码

# 输出结果

left: 0
right: 200
top: 161
bottom: 361
x: 0.0
y: 161.0

绝对位置相关方法：getLocationOnScreen、getLocationInWindow、getGlobalVisibleRect

java 复制代码

ImageView ivTest = findViewById(R.id.iv_test);

int[] locationOnScreen = new int[2];
ivTest.getLocationOnScreen(locationOnScreen);

int[] locationInWindow = new int[2];
ivTest.getLocationInWindow(locationInWindow);

Rect rect = new Rect();
ivTest.getGlobalVisibleRect(rect);

Log.i(TAG, "locationOnScreen: " + Arrays.toString(locationOnScreen));
Log.i(TAG, "locationInWindow: " + Arrays.toString(locationInWindow));
Log.i(TAG, "rect: " + rect);

复制代码

# 输出结果

locationOnScreen: [0, 0]
locationInWindow: [0, 0]
rect: Rect(0, 0 - 0, 0)

java 复制代码

// 使用 View.post 方法处理后

ImageView ivTest = findViewById(R.id.iv_test);

ivTest.post(() -> {
    int[] locationOnScreen = new int[2];
    ivTest.getLocationOnScreen(locationOnScreen);

    int[] locationInWindow = new int[2];
    ivTest.getLocationInWindow(locationInWindow);

    Rect rect = new Rect();
    ivTest.getGlobalVisibleRect(rect);

    Log.i(TAG, "locationOnScreen: " + Arrays.toString(locationOnScreen));
    Log.i(TAG, "locationInWindow: " + Arrays.toString(locationInWindow));
    Log.i(TAG, "rect: " + rect);
});

复制代码

# 输出结果

locationOnScreen: [0, 161]
locationInWindow: [0, 161]
rect: Rect(0, 161 - 200, 361)