以编程方式初始化和设置Button的参数

Question

我试图初始化并以编程方式设置5个按钮的高度和宽度。以下是我的代码，XML和LogCat。

public class Puzzle extends Activity { 

    Button btn1, btn2, btn3, btn4, btn5; 

    @Override 
    protected void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.z1to5); 

     RelativeLayout relativelayout = (RelativeLayout)findViewById(R.id.relativelayout); 
     RelativeLayout.LayoutParams params = new RelativeLayout.LayoutParams(50, 50); 

     btn1 = (Button)findViewById(R.id.btn1); 
     btn2 = (Button)findViewById(R.id.btn2); 
     btn3 = (Button)findViewById(R.id.btn3); 
     btn4 = (Button)findViewById(R.id.btn4); 
     btn5 = (Button)findViewById(R.id.btn5); 

     btn1.setLayoutParams(params); 
     btn2.setLayoutParams(params); 
     btn3.setLayoutParams(params); 
     btn4.setLayoutParams(params); 
     btn5.setLayoutParams(params); 

     relativelayout.addView(btn1); 
     relativelayout.addView(btn2); 
     relativelayout.addView(btn3); 
     relativelayout.addView(btn4); 
     relativelayout.addView(btn5); 
    } 
} 

<RelativeLayout 
    xmlns:android="http://schemas.android.com/apk/res/android" 
    xmlns:tools="http://schemas.android.com/tools" 
    android:id="@+id/relativelayout" 
    android:layout_width="match_parent" 
    android:layout_height="match_parent" > 

    <Button 
     android:id="@+id/btn1" /> 

    <Button 
     android:id="@+id/btn2" /> 

    <Button 
     android:id="@+id/btn3" /> 

    <Button 
     android:id="@+id/btn4" /> 

    <Button 
     android:id="@+id/btn5" /> 
</RelativeLayout> 

这是我第一次尝试在Java中进行布局。我一直都是用XML来完成的。下面是我得到的LogCat错误。

logcat的

11-21 17:22:13.590: E/AndroidRuntime(2639): Process: matt.lyons.tileslider, PID: 2639 
11-21 17:22:13.590: E/AndroidRuntime(2639): java.lang.RuntimeException: Unable to start activity ComponentInfo{matt.lyons.tileslider/matt.lyons.tileslider.Puzzle}: java.lang.RuntimeException: Binary XML file line #8: You must supply a layout_width attribute. 
11-21 17:22:13.590: E/AndroidRuntime(2639):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2176) 
11-21 17:22:13.590: E/AndroidRuntime(2639):  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:2226) 
11-21 17:22:13.590: E/AndroidRuntime(2639):  at android.app.ActivityThread.access$700(ActivityThread.java:135) 
11-21 17:22:13.590: E/AndroidRuntime(2639):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1397) 
11-21 17:22:13.590: E/AndroidRuntime(2639):  at android.os.Handler.dispatchMessage(Handler.java:102) 
11-21 17:22:13.590: E/AndroidRuntime(2639):  at android.os.Looper.loop(Looper.java:137) 
11-21 17:22:13.590: E/AndroidRuntime(2639):  at android.app.ActivityThread.main(ActivityThread.java:4998) 
11-21 17:22:13.590: E/AndroidRuntime(2639):  at java.lang.reflect.Method.invokeNative(Native Method) 
11-21 17:22:13.590: E/AndroidRuntime(2639):  at java.lang.reflect.Method.invoke(Method.java:515) 
11-21 17:22:13.590: E/AndroidRuntime(2639):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:777) 
11-21 17:22:13.590: E/AndroidRuntime(2639):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:593) 
11-21 17:22:13.590: E/AndroidRuntime(2639):  at dalvik.system.NativeStart.main(Native Method) 
11-21 17:22:13.590: E/AndroidRuntime(2639): Caused by: java.lang.RuntimeException: Binary XML file line #8: You must supply a layout_width attribute. 
11-21 17:22:13.590: E/AndroidRuntime(2639):  at android.content.res.TypedArray.getLayoutDimension(TypedArray.java:492) 
11-21 17:22:13.590: E/AndroidRuntime(2639):  at android.view.ViewGroup$LayoutParams.setBaseAttributes(ViewGroup.java:5948) 
11-21 17:22:13.590: E/AndroidRuntime(2639):  at android.view.ViewGroup$MarginLayoutParams.<init>(ViewGroup.java:6117) 
11-21 17:22:13.590: E/AndroidRuntime(2639):  at android.widget.RelativeLayout$LayoutParams.<init>(RelativeLayout.java:1225) 
11-21 17:22:13.590: E/AndroidRuntime(2639):  at android.widget.RelativeLayout.generateLayoutParams(RelativeLayout.java:1062) 
11-21 17:22:13.590: E/AndroidRuntime(2639):  at android.widget.RelativeLayout.generateLayoutParams(RelativeLayout.java:82) 
11-21 17:22:13.590: E/AndroidRuntime(2639):  at android.view.LayoutInflater.rInflate(LayoutInflater.java:757) 
11-21 17:22:13.590: E/AndroidRuntime(2639):  at android.view.LayoutInflater.inflate(LayoutInflater.java:492) 
11-21 17:22:13.590: E/AndroidRuntime(2639):  at android.view.LayoutInflater.inflate(LayoutInflater.java:397) 
11-21 17:22:13.590: E/AndroidRuntime(2639):  at android.view.LayoutInflater.inflate(LayoutInflater.java:353) 
11-21 17:22:13.590: E/AndroidRuntime(2639):  at com.android.internal.policy.impl.PhoneWindow.setContentView(PhoneWindow.java:290) 
11-21 17:22:13.590: E/AndroidRuntime(2639):  at android.app.Activity.setContentView(Activity.java:1928) 
11-21 17:22:13.590: E/AndroidRuntime(2639):  at matt.lyons.tileslider.Puzzle.onCreate(Puzzle.java:17) 
11-21 17:22:13.590: E/AndroidRuntime(2639):  at android.app.Activity.performCreate(Activity.java:5243) 
11-21 17:22:13.590: E/AndroidRuntime(2639):  at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1087) 
11-21 17:22:13.590: E/AndroidRuntime(2639):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:2140) 
11-21 17:22:13.590: E/AndroidRuntime(2639):  ... 11 more 

我在做什么错？

Answer 1

如果要以编程方式创建视图，请不要在layoutId参数中使用方法setContentView（），因为它会调用LayoutInflater从XML文件创建视图，并且无法执行此操作，因为您的XML不正确。所以试试这样：

@Override 
protected void onCreate(Bundle savedInstanceState) { 
    super.onCreate(savedInstanceState); 

    LinearLayout rootLayout = new LinearLayout(getApplicationContext()); 
    rootLayout.setOrientation(LinearLayout.VERTICAL); 

    //Convert DIPs to Pixels 
    int dp = 50; 
    int px = (int) TypedValue.applyDimension(TypedValue.COMPLEX_UNIT_DIP, dp, getResources().getDisplayMetrics()); 

    LinearLayout.LayoutParams layoutParams = new LinearLayout.LayoutParams(px * 4, px); 

    for (int i = 1; i < 6; i++) { 
     Button button = new Button(getApplicationContext()); 
     button.setLayoutParams(layoutParams); 
     button.setText("Button " + i); 
     rootLayout.addView(button); 
    } 

    setContentView(rootLayout); 
}