創建課程並傳遞內容

Question

我做了一個方法，其中所有的字體都得到了更改，但問題是我想使用該方法一次，因此我不必將其複製並粘貼到每個腳本中。

代碼示例：

public void changeFont(){ 

    int[] id_et = {R.id.inputObjectName, R.id.inputObjectValue}; 
    int[] id_tv = {R.id.headerUserInfo, R.id.headerUserPW, R.id.headerUserGW}; 
    int[] id_btn = {R.id.privBtnIncome, R.id.privBtnExpense}; 

    Typeface font = Typeface.createFromAsset(getAssets(), "Sanford.TTF"); 

    for(int i = 0; i < id_et.length; i++){ 
     EditText textbox = (EditText) findViewById(id_et[i]); 
     textbox.setTypeface(font); 
    } 

    for(int i = 0; i < id_tv.length; i++){ 
     TextView tv = (TextView) findViewById(id_tv[i]); 
     tv.setTypeface(font); 
    } 

    for(int i = 0; i < id_btn.length; i++){ 
     Button btn = (Button) findViewById(id_btn[i]); 
     btn.setTypeface(font); 
    } 

} 

當我創建一個類，使一個物體使用構造函數來獲取數據，程序崩潰。

這是類的樣子：

public class ChangeFont extends Activity{ 
    public ChangeFont(){ 

    int[] id_et = {R.id.inputObjectName, R.id.inputObjectValue}; 
    int[] id_tv = {R.id.headerUserInfo, R.id.headerUserPW, R.id.headerUserGW}; 
    int[] id_btn = {R.id.privBtnIncome, R.id.privBtnExpense}; 

    Typeface font = Typeface.createFromAsset(getAssets(), "Sanford.TTF"); 

    for(int i = 0; i < id_et.length; i++){ 
     EditText textbox = (EditText) findViewById(id_et[i]); 
     textbox.setTypeface(font); 
    } 

    for(int i = 0; i < id_tv.length; i++){ 
     TextView tv = (TextView) findViewById(id_tv[i]); 
     tv.setTypeface(font); 
    } 

    for(int i = 0; i < id_btn.length; i++){ 
     Button btn = (Button) findViewById(id_btn[i]); 
     btn.setTypeface(font); 
    } 

    } 

} 

錯誤日誌：

12-12 17:23:49.746: E/AndroidRuntime(6159): FATAL EXCEPTION: main 
12-12 17:23:49.746: E/AndroidRuntime(6159): java.lang.RuntimeException: Unable to start activity ComponentInfo{united.aristal.freewallet/united.aristal.freewallet.PrivateWallet}: java.lang.NullPointerException 
12-12 17:23:49.746: E/AndroidRuntime(6159):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1955) 
12-12 17:23:49.746: E/AndroidRuntime(6159):  at android.app.ActivityThread.handleLaunchActivity(ActivityThread.java:1980) 
12-12 17:23:49.746: E/AndroidRuntime(6159):  at android.app.ActivityThread.access$600(ActivityThread.java:122) 
12-12 17:23:49.746: E/AndroidRuntime(6159):  at android.app.ActivityThread$H.handleMessage(ActivityThread.java:1146) 
12-12 17:23:49.746: E/AndroidRuntime(6159):  at android.os.Handler.dispatchMessage(Handler.java:99) 
12-12 17:23:49.746: E/AndroidRuntime(6159):  at android.os.Looper.loop(Looper.java:137) 
12-12 17:23:49.746: E/AndroidRuntime(6159):  at android.app.ActivityThread.main(ActivityThread.java:4340) 
12-12 17:23:49.746: E/AndroidRuntime(6159):  at java.lang.reflect.Method.invokeNative(Native Method) 
12-12 17:23:49.746: E/AndroidRuntime(6159):  at java.lang.reflect.Method.invoke(Method.java:511) 
12-12 17:23:49.746: E/AndroidRuntime(6159):  at com.android.internal.os.ZygoteInit$MethodAndArgsCaller.run(ZygoteInit.java:784) 
12-12 17:23:49.746: E/AndroidRuntime(6159):  at com.android.internal.os.ZygoteInit.main(ZygoteInit.java:551) 
12-12 17:23:49.746: E/AndroidRuntime(6159):  at dalvik.system.NativeStart.main(Native Method) 
12-12 17:23:49.746: E/AndroidRuntime(6159): Caused by: java.lang.NullPointerException 
12-12 17:23:49.746: E/AndroidRuntime(6159):  at android.content.ContextWrapper.getAssets(ContextWrapper.java:75) 
12-12 17:23:49.746: E/AndroidRuntime(6159):  at united.aristal.freewallet.ChangeFont.<init>(ChangeFont.java:16) 
12-12 17:23:49.746: E/AndroidRuntime(6159):  at united.aristal.freewallet.PrivateWallet.onCreate(PrivateWallet.java:32) 
12-12 17:23:49.746: E/AndroidRuntime(6159):  at android.app.Activity.performCreate(Activity.java:4465) 
12-12 17:23:49.746: E/AndroidRuntime(6159):  at android.app.Instrumentation.callActivityOnCreate(Instrumentation.java:1049) 
12-12 17:23:49.746: E/AndroidRuntime(6159):  at android.app.ActivityThread.performLaunchActivity(ActivityThread.java:1919) 
12-12 17:23:49.746: E/AndroidRuntime(6159):  ... 11 more 

因此，誰能幫助我在這裏？

Answer 1

getAssets因爲您創建了ChangeFont實例而不是讓Android執行此操作，因此拋出了NullPointerException。如果ChangeFont只是一個工具類，它不應該延伸Activity。

而是使用實際活動的實例初始化它，然後讓它調用該活動的方法。

public class ChangeFont { 

    public ChangeFont(final Activity activity) { 
     this.activity = activity; 

     Typeface font = Typeface.createFromAsset(activity.getAssets(), "Sanford.TTF"); 
    } 

}