擴展TextView不出現

Question

以下代碼假設要這樣做：
- 使用標準TextView顯示字符串
- 使用擴展TextView顯示字符串。 （這個覆蓋了OnDraw並在字符串上畫了一條線，使其看起來像被刪除了）

問題是隻有標準顯示。

請檢查下面的代碼：

ExpenseWatchActivity.java（這是主要的活性）

package com.app.expensewatch; 

import android.app.Activity; 
import android.os.Bundle; 
import android.widget.TextView; 
import java.util.Calendar; 

public class ExpenseWatchActivity extends Activity { 

    /** Called when the activity is first created. */ 
    @Override 
    public void onCreate(Bundle savedInstanceState) { 
     super.onCreate(savedInstanceState); 
     setContentView(R.layout.main); 

     int day,mon,yr; 

     Calendar cal = Calendar.getInstance(); 

     day = cal.get(Calendar.DATE); 
     mon = 1 + cal.get(Calendar.MONTH); 
     yr = cal.get(Calendar.YEAR); 

     String text = getResources().getString(R.string.hello, day , mon , yr); 

     TextView tx1 = (TextView)findViewById(R.id.text1); 
     tx1.setText(text); 

     List1 list = (List1)findViewById(R.id.list1); 
     list.setText(text); 
    } 
} 

List1.java（這是擴展的TextView）

package com.app.expensewatch; 

import android.util.AttributeSet; 
import android.widget.TextView; 
import android.content.Context; 
import android.graphics.Canvas; 
import android.graphics.Paint; 
import com.app.expensewatch.R; 

public class List1 extends TextView { 

    public List1(Context context) { 
     super(context); 
    } 

    public List1(Context context, AttributeSet attrs) { 
     super(context, attrs); 
    } 

    public List1(Context context, AttributeSet attrs, int defStyle) { 
     super(context, attrs, defStyle); 
    } 

    float ht = (float)getHeight(); 
    float wd = (float)getWidth(); 

    @Override 
    protected void onDraw(Canvas canvas) 
    { 
     Paint divider = new Paint(); 
     divider.setColor(getResources().getColor(R.color.line1)); 
     canvas.drawLine(0,ht/2,wd,ht/2,divider); 
    } 
} 

主。 xml

<?xml version="1.0" encoding="utf-8"?> 
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android" 
    android:layout_width="fill_parent" 
    android:layout_height="fill_parent" 
    android:orientation="vertical" > 

    <TextView 
     android:id="@+id/text1" 
     android:layout_width="wrap_content" 
     android:layout_height="wrap_content" 
     android:text="@string/hello" /> 

    <com.app.expensewatch.List1 
     android:id="@+id/list1" 
     android:layout_width="wrap_content" 
     android:layout_height="wrap_content" 
     android:text="@string/hello" /> 
     /> 
</LinearLayout> 

的strings.xml

<?xml version="1.0" encoding="utf-8"?> 
<resources> 

    <string name="app_name">ExpenseWatch</string> 
    <string name="hello">Today is : %1$d/%2$d/%3$d</string> 

</resources> 

colors.xml

<?xml version="1.0" encoding="utf-8"?> 
<resources> 

    <color name="line1">#6456648f</color> 

</resources> 

Answer 1

當您設置在擴展TextView的寬度和高度，認爲尚未測量。它的寬度和高度都是零。在擴展的TextView中重寫onMeasure（），並在其中設置寬度和高度。

protected void onMeasure (int widthMeasureSpec, int heightMeasureSpec) { 
    super.onMeasure(widthMeasureSpec, heightMeasureSpec); 
    ht = getHeight(); 
    wd = getWidth();  
} 

總是要避免設置一個私有變量，該變量將在視圖中保存維度，直到調用onMeasure（）之後。