图像视图旋转时应用程序崩溃

Question

大家好，我是 android 开发新手，我正在尝试旋转图像视图。当（显然）我按下按钮并且应用程序自行关闭时，问题就来了代码java：包 comad.exampleaaaa.vittoriodaadntico.bottiglia3;

import android.support.v7.app.AppCompatActivity;
import android.os.Bundle;
import android.view.Menu;
import android.view.MenuItem;
import android.view.View;
import android.view.animation.Animation;
import android.view.animation.LinearInterpolator;
import android.view.animation.RotateAnimation;
import android.widget.Button;
import android.widget.ImageView;

public class MainActivity6 extends AppCompatActivity {
public ImageView bottiglia;
public Button gira;

@Override
protected void onCreate(Bundle savedInstanceState) {
    gira=(Button)findViewById(R.id.btn_roll);
    bottiglia=(ImageView)findViewById(R.id.bottiglia);
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main6);

}
public void rollOnClick(View v){
    RotateAnimation anim=new RotateAnimation(0,360,20,20,20,20);
    anim.setInterpolator(new LinearInterpolator());
    anim.setRepeatCount(Animation.INFINITE);
   anim.setDuration(700);
    bottiglia.startAnimation(anim);


}
@Override
public boolean onCreateOptionsMenu(Menu menu) {
    // Inflate the menu; this adds items to the action bar if it is present.
    getMenuInflater().inflate(R.menu.menu_main_activity6, menu);
    return true;
}

@Override
public boolean onOptionsItemSelected(MenuItem item) {
    // Handle action bar item clicks here. The action bar will
    // automatically handle clicks on the Home/Up button, so long
    // as you specify a parent activity in AndroidManifest.xml.
    int id = item.getItemId();

    //noinspection SimplifiableIfStatement
    if (id == R.id.action_settings) {
        return true;
    }

    return super.onOptionsItemSelected(item);
}
}

错误日志： http://imgur.com/H2Phsvf

Answer 1

您调用方法的顺序错误：

@Override
protected void onCreate(Bundle savedInstanceState) {
    gira=(Button)findViewById(R.id.btn_roll); // This
    bottiglia=(ImageView)findViewById(R.id.bottiglia); // And this
    super.onCreate(savedInstanceState);
    setContentView(R.layout.activity_main6); // Should come after this
}

在设置内容视图之前在这里搜索视图。您应该设置视图，然后才搜索小部件。否则无法找到您的小部件的视图，因此 gira 和 bottiglia 都是 nulls:

@Override protected void onCreate(Bundle savedInstanceState) { super.onCreate(savedInstanceState); setContentView(R.layout.activity_main6); gira=(Button)findViewById(R.id.btn_roll); bottiglia=(ImageView)findViewById(R.id.bottiglia); }

图像视图旋转时应用程序崩溃

app chrashing on imageview rotation

android

imageview