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我正在尝试在 onCreate() 期间自定义相对布局并且遇到问题，因为 ImageView 的 getWidth() 和 getHeight() 属性返回零。这里有几个线程说这是因为还没有绘制布局，所以现在知道实际的图像尺寸还为时过早。

我应该在生命周期的哪个阶段执行此操作？

这就是我要完成的工作，而无需对图像宽度进行硬编码：

在此处输入图像描述

这是应用程序的布局：

<?xml version="1.0" encoding="utf-8"?>
<RelativeLayout xmlns:android="http://schemas.android.com/apk/res/android"
    xmlns:tools="http://schemas.android.com/tools"
    android:layout_width="match_parent"
    android:layout_height="match_parent"
    tools:context=".MainActivity" 
    android:background="#44000000"
    >

    <RelativeLayout 
        android:id="@+id/bannerAdLayout"
        android:layout_width="match_parent"
        android:layout_height="wrap_content"
        android:layout_alignParentBottom="true"
        android:layout_marginBottom="60dip"
        android:orientation="horizontal"
        android:clickable="true"
        android:background="#00000000"
        >

       <LinearLayout android:id="@+id/bannerAdActionButtonLayout" 
            android:orientation="vertical"
            android:layout_width="match_parent"
            android:layout_height="wrap_content"
            android:layout_alignParentLeft="true"
            android:background="#ff00ff00"
            >
            <!-- NOTE: image's left margin set at run-time -->
            <ImageView android:id="@+id/bannerAdThumbnail"
                android:contentDescription=""
                android:layout_width="wrap_content"
                android:layout_height="wrap_content"
                android:src="@drawable/ic_launcher"
                />
        </LinearLayout>

        <!-- NOTE: layout's left margin set to 50% of screen width at run-time -->
        <LinearLayout android:id="@+id/bannerAdTextLayout" 
                android:orientation="vertical"
                android:layout_width="match_parent"
                android:layout_height="wrap_content"
                android:layout_alignParentLeft="true"
                android:background="#ffffffff"
                >
                <TextView android:id="@+id/bannerAdInstructions"
                    android:layout_width="match_parent"
                    android:layout_height="wrap_content"
                    android:gravity="left"
                    android:text="First line of text"
                    />
                <TextView android:id="@+id/bannerAdTitle"
                    android:layout_width="match_parent"
                    android:layout_height="wrap_content"
                    android:gravity="left"
                    android:text="Second line of text"
                    />
        </LinearLayout>        
    </RelativeLayout>
</RelativeLayout>

以及 onCreate() 中的代码来自定义布局并设置 imageview 的左边距，使其位于中心的左侧：

private Context mThisActivityContext = null;
private Resources mResources = null;

private ImageView mBannerAdImage = null;
private TextView mBannerAdLabel = null;
private TextView mBannerAdOffer = null;
private RelativeLayout mBannerAdLayout = null;
int mBannerAdImageWidth = 48;  // set a default width

// Screen dimensions
private int mScreenHeight;
private int mScreenWidth;

@Override
protected void onCreate(Bundle savedInstanceState) {
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main);

    mThisActivityContext = MainActivity.this;
    mResources = mThisActivityContext.getResources();

    setContentView(R.layout.activity_main);
    setRequestedOrientation(ActivityInfo.SCREEN_ORIENTATION_PORTRAIT);

    // get screen dimensions
    mScreenHeight = mThisActivityContext.getResources().getDisplayMetrics().heightPixels;
    mScreenWidth = mThisActivityContext.getResources().getDisplayMetrics().widthPixels;
    Log.w(TAG, String.format("Device screen dimensions are: %d w x %d h", mScreenWidth, mScreenHeight));

        // get the banner ad layout
    mBannerAdLayout = (RelativeLayout)findViewById(R.id.bannerAdLayout);
    // get the image to use for the banner ad
    mBannerAdImage = (ImageView)findViewById(R.id.bannerAdThumbnail);
    GetImageFromAsset(mResources, mBannerAdImage, "ic_launcher");
    Log.w(TAG, String.format("Image ic_launcher dimensions are %d W x %d H", mBannerAdImage.getWidth(), mBannerAdImage.getHeight()));

    // get the banner ad TextView controls
    mBannerAdLabel = ((TextView)findViewById(R.id.bannerAdInstructions)); 
    mBannerAdOffer = ((TextView)findViewById(R.id.bannerAdTitle)); 

    // initialize the banner ad layout
    initBannerAdLayout();
}

    // set an image's bitmap from the specified asset
private void GetImageFromAsset(Resources res, ImageView image, String assetName) {
    try {
        int drawableId = res.getIdentifier(assetName, "drawable", "com.example.animationtest");
        Bitmap bMap = BitmapFactory.decodeResource(res, drawableId);
        image.setImageBitmap(bMap);
            if (image.getWidth() > 0) {
                mBannerAdImageWidth = image.getWidth();
            } 
    }
    catch (Exception e) {
        Log.e(TAG, "Failure to get drawable id for " + assetName, e);
    }
}

// initialize the Banner Ad layout based on the screen dimensions
private void initBannerAdLayout() {
    // reset the background color
    mBannerAdLayout.setBackgroundColor(Color.TRANSPARENT);

    // use margin layout parameters to set the position of the action button within its LinearLayout
    int marginLeft = (int)(mScreenWidth * 0.5) - mBannerAdImageWidth;
    MarginLayoutParams params = (MarginLayoutParams)mBannerAdImage.getLayoutParams(); 
    params.setMargins(marginLeft, 0, 0, 0); 
    mBannerAdImage.setLayoutParams(params);
    Log.w(TAG, String.format("Image left margin is %d, image width is %d", marginLeft, mBannerAdImage.getWidth()));  // xxx

    // use margin layout parameters to set the position of the inner text LinearLayout
    LinearLayout bannerAdTextLayout = (LinearLayout)findViewById(R.id.bannerAdTextLayout);
    marginLeft = (int)(mScreenWidth * 0.5);
    params = (MarginLayoutParams)bannerAdTextLayout.getLayoutParams(); 
    params.setMargins(marginLeft, 0, 0, 0); 
    bannerAdTextLayout.setLayoutParams(params);
    Log.w(TAG, String.format("Text layout left margin is %d", marginLeft));

    mBannerAdLayout.invalidate();
}
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2 回答 2

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（放弃了我的第一个答案，实际上已经看过你想要做什么）

给bannerAdActionButtonLayout LinearLayout（拥有ImageView孩子的）以下属性android:layout_centerInParent="true"，然后将后续RelativeLayout（bannerAdTextLayout）设置在该属性的右侧android:layout_toRightOf="@id/bannerAdActionButtonLayout"。

于 2013-06-24T20:32:49.423 回答
0

从可绘制资源创建位图。

Bitmap bitmap = BitmapFactory.decodeResource(getResources(), R.drawable.ic_launcher);

获得位图后，您可以通过 bitmap.getWidth() 和 bitmap.getHeight() 获取图像尺寸。

于 2013-06-24T20:10:58.693 回答