Java 如何在Android中以编程方式添加多个自定义视图
我这里有个小问题。 我已经创建了一个自定义视图类,它承载一些数据,我正在尝试在我的主活动中动态添加它,现在当我尝试添加单个视图时,它工作得很好。但是当我把它放在for循环中,假设我想添加多个时,代码会因以下错误而中断:Java 如何在Android中以编程方式添加多个自定义视图,java,android,android-layout,for-loop,android-custom-view,Java,Android,Android Layout,For Loop,Android Custom View,我这里有个小问题。 我已经创建了一个自定义视图类,它承载一些数据,我正在尝试在我的主活动中动态添加它,现在当我尝试添加单个视图时,它工作得很好。但是当我把它放在for循环中,假设我想添加多个时,代码会因以下错误而中断: java.lang.RuntimeException: Unable to start activity ComponentInfo{com.digiart.xapp/com.digiart.xapp.MainActivity}: java.lang.NullPointerExc
java.lang.RuntimeException: Unable to start activity ComponentInfo{com.digiart.xapp/com.digiart.xapp.MainActivity}: java.lang.NullPointerException: Attempt to invoke virtual method 'void android.widget.RelativeLayout.addView(android.view.View)' on a null object reference
自定义视图:
public class TableView extends View {
private static final String TAG = "TableView";
private int numberOfSeats;
private int tableId;
private int positionX;
private int positionY;
private int objectWidth;
private int objectHeight;
private boolean isTaken;
private String tableKind;
private Rect rectangle;
private Paint paint;
public TableView(Context context, AttributeSet attrs) {
super(context, attrs);
}
public TableView(Context context,int numberOfSeats,int tableId,int positionX,int positionY,int width,int height
,boolean isTaken, String tableKind) {
super(context);
this.numberOfSeats = numberOfSeats;
this.tableId = tableId;
this.positionX = positionX;
this.positionY = positionY;
this.objectWidth = width;
this.objectHeight = height;
this.isTaken = isTaken;
this.tableId = tableId;
this.tableKind = tableKind;
//defining shape
rectangle = new Rect(positionX,positionY,width,height);
//defining shape color
paint = new Paint();
paint.setColor(Color.GRAY);
Log.i(TAG, "TableView: tableId: "+tableId+" isTaken: "+isTaken);
}
@Override
protected void onDraw(Canvas canvas) {
super.onDraw(canvas);
//canvas.drawColor(Color.BLUE);
canvas.drawRect(rectangle, paint);
}
public int getNumberOfSeats() {
return numberOfSeats;
}
public int getTableId() {
return tableId;
}
public int getPositionX() {
return positionX;
}
public int getPositionY() {
return positionY;
}
public int getObjectWidth() {
return objectWidth;
}
public int getObjectHeight() {
return objectHeight;
}
public boolean isTaken() {
return isTaken;
}
public String getTableKind() {
return tableKind;
}
}
来自主活动的代码段,带有一些用于测试的静态值:
for (int i = 0;i<15;i++) {
tv = new TableView(MainActivity.this, numberOfSeats, tableId, positionX, positionY, objectWidth, objectHeight
, isTaken, tableKind);
positionX +=20;
floorPlan.addView(tv);
}
for(int i=0;i问题正是错误所说的:
Attempt to invoke method addView(android.view.View)' on a null object reference
您正在尝试执行null.addView,这导致了错误
在代码中执行“添加视图”的唯一时间如下:
floorPlan.addView(tv);
这意味着floorPlan==null
检查初始化平面布置图的位置并确保其设置正确:)是的,我刚刚意识到。。。Lol:D谢谢你的回答,它是正确的:D