Android runOnUiThread中TextView上的NullPointerException
所以我有以下代码:Android runOnUiThread中TextView上的NullPointerException,android,multithreading,nullpointerexception,Android,Multithreading,Nullpointerexception,所以我有以下代码: public class TargetActivity extends Activity { protected MySurfaceView mActivity; public TextView Text = null; /** Called when the activity is first created. */ @Override public void onCreate(Bundle savedInstanceState) {
public class TargetActivity extends Activity {
protected MySurfaceView mActivity;
public TextView Text = null;
/** Called when the activity is first created. */
@Override
public void onCreate(Bundle savedInstanceState) {
super.onCreate(savedInstanceState);
setContentView(R.layout.activity_target);
Text = (TextView) findViewById(R.id.textView1);
}
public void receiveMyMessage()
{
Log.d("Essai", "Test 1");
Text = (TextView) findViewById(R.id.textView1);
Log.d("Essai", "Test 2");
runOnUiThread(new Runnable() {
@Override
public void run() {
if (Text != null) Text.setText("Done");
}
});
}
}
我在线程中调用receiveMyMessage以更改TextView中的文本,但在调用时我遇到以下错误:
01-07 22:13:01.375: D/Essai(31552): Test 1
01-07 22:13:01.406: W/dalvikvm(31552): threadid=9: thread exiting with uncaught exception (group=0x4001f888)
01-07 22:13:01.406: E/AndroidRuntime(31552): FATAL EXCEPTION: Thread-9
01-07 22:13:01.406: E/AndroidRuntime(31552): java.lang.NullPointerException
01-07 22:13:01.406: E/AndroidRuntime(31552): at android.app.Activity.findViewById(Activity.java:1637)
01-07 22:13:01.406: E/AndroidRuntime(31552): at com.mat.archery.statistics.TargetActivity.receiveMyMessage(TargetActivity.java:36)
01-07 22:13:01.406: E/AndroidRuntime(31552): at com.mat.archery.statistics.MySurfaceView.onDraw(MySurfaceView.java:133)
01-07 22:13:01.406: E/AndroidRuntime(31552): at com.mat.archery.statistics.MySurfaceThread.run(MySurfaceThread.java:43)
第36行是:Text=(TextView)findViewById(R.id.textView1)代码>
我不明白为什么它是空指针,如果我对行进行注释,则没有错误,但TextView没有更改,因此文本为空
如果有帮助,以下是布局:
<?xml version="1.0" encoding="utf-8"?>
<LinearLayout xmlns:android="http://schemas.android.com/apk/res/android"
android:orientation="vertical"
android:layout_width="fill_parent"
android:layout_height="fill_parent">
<TextView
android:id="@+id/textView1"
android:layout_width="match_parent"
android:layout_height="wrap_content"
android:text="Test"
android:textAppearance="?android:attr/textAppearanceLarge" />
<FrameLayout
android:layout_width="fill_parent"
android:layout_height="fill_parent">
<com.mat.archery.statistics.MySurfaceView
android:layout_width="fill_parent"
android:layout_height="fill_parent"/>
</FrameLayout>
</LinearLayout>
这就是抽签的地方,在这里,receiveMyMessage是call:
public class MySurfaceView extends SurfaceView implements SurfaceHolder.Callback{
private MySurfaceThread thread;
private Paint paint = new Paint(Paint.ANTI_ALIAS_FLAG);
private Paint paintJaune = new Paint(Paint.ANTI_ALIAS_FLAG);
int cx, cy, offx, offy;
private float initX, initY, radius;
public double distx, disty, distance = 100;
private boolean drawing = true;
private boolean first = true;
public boolean touch = false;
public TextView Text;
protected MySurfaceThread msurfacethread;
public TargetActivity mActivity = null;
public MySurfaceView(Context context) {
super(context);
// TODO Auto-generated constructor stub
init();
}
public MySurfaceView(Context context, AttributeSet attrs) {
super(context, attrs);
// TODO Auto-generated constructor stub
init();
}
public MySurfaceView(Context context, AttributeSet attrs, int defStyle) {
super(context, attrs, defStyle);
// TODO Auto-generated constructor stub
init();
}
private void init(){
Log.d("Essai", "TargetActivity 5");
getHolder().addCallback(this);
thread = new MySurfaceThread(getHolder(), this);
setFocusable(true); // make sure we get key events
paint.setColor(getResources().getColor(R.color.Fleche1Default));
paint.setStyle(Style.FILL);
paintJaune.setColor(getResources().getColor(R.color.Jaune));
paintJaune.setStyle(Style.FILL);
mActivity = new TargetActivity();
Text = (TextView) findViewById(R.id.textView1);
}
@Override
public void surfaceChanged(SurfaceHolder arg0, int arg1, int arg2, int arg3) {
// TODO Auto-generated method stub
drawing = true;
}
@Override
public void surfaceCreated(SurfaceHolder holder) {
// TODO Auto-generated method stub
thread.setRunning(true);
thread.start();
}
@Override
public void surfaceDestroyed(SurfaceHolder holder) {
// TODO Auto-generated method stub
boolean retry = true;
thread.setRunning(false);
while (retry) {
try {
thread.join();
retry = false;
}
catch (InterruptedException e) {
}
}
}
@Override
protected void onDraw(Canvas canvas) {
// TODO Auto-generated method stub
//super.onDraw(canvas);
int width = this.getWidth();
int height = this.getHeight();
if(drawing){
canvas.drawColor(Color.BLACK);
canvas.drawCircle(width/2, height/2, 80, paintJaune);
canvas.drawCircle(initX, initY, radius, paint);
if (touch == true){
distx = (width/2)-initX;
distx *= distx;
disty = (height/2)-initY;
disty *= disty;
distance = distx + disty;
distance = Math.sqrt(distance);
}
if((distance + radius/2) < 40)
{
mActivity.receiveMyMessage();
}
}
}
@Override
public boolean onTouchEvent(MotionEvent event) {
// TODO Auto-generated method stub
//return super.onTouchEvent(event);
int action = event.getAction();
if (action==MotionEvent.ACTION_MOVE){
initX = event.getX();
initY = event.getY();
radius = 30;
drawing = true;
first = false;
touch = true;
}
else if (action==MotionEvent.ACTION_DOWN){
initX = event.getX();
initY = event.getY();
radius = 30;
drawing = true;
first = false;
touch = true;
}
else if (action==MotionEvent.ACTION_UP){
try {
Thread.sleep(50);
} catch (InterruptedException e) {}
drawing = false;
first = false;
touch = false;
}
return true;
}
}
公共类MySurfaceView扩展了SurfaceView,实现了SurfaceHolder.Callback{
私有MySurfaceThread线程;
私有油漆=新油漆(油漆.防油漆别名标志);
私有油漆paintJaune=新油漆(油漆.防油漆别名标志);
内勤cx、cy、offx、offy;
私有浮点initX、initY、radius;
公共双距离,距离,距离=100;
私有布尔图形=真;
private boolean first=true;
公共布尔触摸=假;
公共文本查看文本;
受保护的MySurfaceThread msurfacethread;
公共目标活动mActivity=null;
公共MySurfaceView(上下文){
超级(上下文);
//TODO自动生成的构造函数存根
init();
}
公共MySurfaceView(上下文、属性集属性){
超级(上下文,attrs);
//TODO自动生成的构造函数存根
init();
}
公共MySurfaceView(上下文、属性集属性、int-defStyle){
超级(上下文、属性、定义样式);
//TODO自动生成的构造函数存根
init();
}
私有void init(){
Log.d(“Essai”、“目标活动5”);
getHolder().addCallback(此);
thread=newmysurfacethread(getHolder(),this);
setFocusable(true);//确保获取关键事件
setColor(getResources().getColor(R.color.Fleche1Default));
油漆.设置样式(样式.填充);
setColor(getResources().getColor(R.color.Jaune));
paintJaune.setStyle(Style.FILL);
mActivity=新的TargetActivity();
Text=(TextView)findViewById(R.id.textView1);
}
@凌驾
公共无效表面更改(表面更改arg0、int arg1、int arg2、int arg3){
//TODO自动生成的方法存根
绘图=真;
}
@凌驾
已创建的公共空白表面(表面持有人){
//TODO自动生成的方法存根
thread.setRunning(true);
thread.start();
}
@凌驾
公共空间表面覆盖(表面覆盖物持有人){
//TODO自动生成的方法存根
布尔重试=真;
thread.setRunning(false);
while(重试){
试一试{
thread.join();
重试=错误;
}
捕捉(中断异常e){
}
}
}
@凌驾
受保护的void onDraw(画布){
//TODO自动生成的方法存根
//super.onDraw(帆布);
int width=this.getWidth();
int height=this.getHeight();
if(图纸){
画布。drawColor(颜色。黑色);
画布.画圈(宽/2,高/2,80,画圈);
画布.画圈(初始、初始、半径、绘制);
if(touch==true){
distx=(宽度/2)-initX;
distx*=distx;
距离=(高度/2)-距离;
disty*=disty;
距离=distx+disty;
距离=数学sqrt(距离);
}
如果((距离+半径/2)<40)
{
mActivity.receiveMyMessage();
}
}
}
@凌驾
公共布尔onTouchEvent(运动事件){
//TODO自动生成的方法存根
//返回super.onTouchEvent(事件);
int action=event.getAction();
if(action==MotionEvent.action\u MOVE){
initX=event.getX();
initY=event.getY();
半径=30;
绘图=真;
第一个=假;
触摸=真实;
}
else if(action==MotionEvent.action\u DOWN){
initX=event.getX();
initY=event.getY();
半径=30;
绘图=真;
第一个=假;
触摸=真实;
}
else if(action==MotionEvent.action\u UP){
试一试{
睡眠(50);
}捕获(中断异常e){}
图纸=假;
第一个=假;
触摸=假;
}
返回true;
}
}
这就是让你绊倒的原因
mActivity=newtargetactivity()代码>
你不能那样做。只有系统可以实例化活动
你也许能逃脱<代码>mActivity=(TargetActivity)getContext()代码>
我不想再提了,但它会解决你眼前的问题
您应该考虑使用广播意图发送消息。
getContext().sendBroadcast(新意图(“绘图完成”)代码>
在这种情况下,您必须实现自己的广播接收器 在onCreate中找到TextView之后,为什么还要再次尝试查找它?这可能与调用活动的显式构造函数有关。无论如何,findViewById()
不应该抛出npe,但它可以返回null,堆栈跟踪是否还说了什么?何时调用receiveMyMessage()
?findViewById
中唯一的null
是如果getWindow()
为null。我认为A--C是对的;几乎可以肯定的是,显式调用活动的构造函数是导致问题的原因。绘图(代码的第三部分)中调用了receiveMyMessage()
,我可以用什么来替换Acivity
?(我是java/android的初学者)据我所知,如果需要更新TargetActivity
中的UI,则通过Intent
发送数据,并创建活动。将该活动中的receiveMyMessage()
函数设为私有函数,并从活动中调用它
public class MySurfaceView extends SurfaceView implements SurfaceHolder.Callback{
private MySurfaceThread thread;
private Paint paint = new Paint(Paint.ANTI_ALIAS_FLAG);
private Paint paintJaune = new Paint(Paint.ANTI_ALIAS_FLAG);
int cx, cy, offx, offy;
private float initX, initY, radius;
public double distx, disty, distance = 100;
private boolean drawing = true;
private boolean first = true;
public boolean touch = false;
public TextView Text;
protected MySurfaceThread msurfacethread;
public TargetActivity mActivity = null;
public MySurfaceView(Context context) {
super(context);
// TODO Auto-generated constructor stub
init();
}
public MySurfaceView(Context context, AttributeSet attrs) {
super(context, attrs);
// TODO Auto-generated constructor stub
init();
}
public MySurfaceView(Context context, AttributeSet attrs, int defStyle) {
super(context, attrs, defStyle);
// TODO Auto-generated constructor stub
init();
}
private void init(){
Log.d("Essai", "TargetActivity 5");
getHolder().addCallback(this);
thread = new MySurfaceThread(getHolder(), this);
setFocusable(true); // make sure we get key events
paint.setColor(getResources().getColor(R.color.Fleche1Default));
paint.setStyle(Style.FILL);
paintJaune.setColor(getResources().getColor(R.color.Jaune));
paintJaune.setStyle(Style.FILL);
mActivity = new TargetActivity();
Text = (TextView) findViewById(R.id.textView1);
}
@Override
public void surfaceChanged(SurfaceHolder arg0, int arg1, int arg2, int arg3) {
// TODO Auto-generated method stub
drawing = true;
}
@Override
public void surfaceCreated(SurfaceHolder holder) {
// TODO Auto-generated method stub
thread.setRunning(true);
thread.start();
}
@Override
public void surfaceDestroyed(SurfaceHolder holder) {
// TODO Auto-generated method stub
boolean retry = true;
thread.setRunning(false);
while (retry) {
try {
thread.join();
retry = false;
}
catch (InterruptedException e) {
}
}
}
@Override
protected void onDraw(Canvas canvas) {
// TODO Auto-generated method stub
//super.onDraw(canvas);
int width = this.getWidth();
int height = this.getHeight();
if(drawing){
canvas.drawColor(Color.BLACK);
canvas.drawCircle(width/2, height/2, 80, paintJaune);
canvas.drawCircle(initX, initY, radius, paint);
if (touch == true){
distx = (width/2)-initX;
distx *= distx;
disty = (height/2)-initY;
disty *= disty;
distance = distx + disty;
distance = Math.sqrt(distance);
}
if((distance + radius/2) < 40)
{
mActivity.receiveMyMessage();
}
}
}
@Override
public boolean onTouchEvent(MotionEvent event) {
// TODO Auto-generated method stub
//return super.onTouchEvent(event);
int action = event.getAction();
if (action==MotionEvent.ACTION_MOVE){
initX = event.getX();
initY = event.getY();
radius = 30;
drawing = true;
first = false;
touch = true;
}
else if (action==MotionEvent.ACTION_DOWN){
initX = event.getX();
initY = event.getY();
radius = 30;
drawing = true;
first = false;
touch = true;
}
else if (action==MotionEvent.ACTION_UP){
try {
Thread.sleep(50);
} catch (InterruptedException e) {}
drawing = false;
first = false;
touch = false;
}
return true;
}
}