Android Dialog崩溃

Question

你好，我是android编程的初学者，这是我在这个论坛上的第一篇文章，我有一个问题。当我打开它时，应用程序崩溃了。如果你按下按钮然后出现一个对话框屏幕，如果按下确定，那么应该是一个显示ok的toast。按钮取消也是如此。按钮是onClick。

 package com.example.dialogfragmenttest;

import android.os.Bundle;
import android.app.Activity;
import android.app.FragmentManager;
import android.view.Menu;
import android.widget.TextView;
import android.widget.Button;
import android.widget.Toast;

public class MainActivity extends Activity {

    Button Button1;
    TextView Textview1;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        Button1 = (Button) findViewById(R.id.button1);
        Textview1 = (Button) findViewById(R.id.Textview1);
    }

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

    public void onClick(){
        FragmentManager manager=getFragmentManager();
        FireMissilesDialogFragment schermpje = new FireMissilesDialogFragment();
        schermpje.show(manager, "mydialog");
    }

    public void ok(){
        Toast.makeText(this, "ok", Toast.LENGTH_LONG).show();
    }

    public void cancel(){
        Toast.makeText(this, "cancel", Toast.LENGTH_LONG).show();
}


package com.example.dialogfragmenttest;

import android.app.AlertDialog;
import android.app.Dialog;
import android.app.DialogFragment;
import android.content.DialogInterface;
import android.os.Bundle;

public class FireMissilesDialogFragment extends DialogFragment {

    @Override
    public Dialog onCreateDialog(Bundle savedInstanceState) {
        // Use the Builder class for convenient dialog construction
        AlertDialog.Builder builder = new AlertDialog.Builder(getActivity());
        builder.setMessage(R.string.message)
               .setPositiveButton(R.string.ok, new DialogInterface.OnClickListener() {
                   public void onClick(DialogInterface dialog, int id) {
                       // ok
                        MainActivity mainactivity = new MainActivity();
                       mainactivity.ok();
                   }
               })
                .setNegativeButton(R.string.cancel, new DialogInterface.OnClickListener() {
                    public void onClick(DialogInterface dialog, int id) {
                        // cancel
                        MainActivity mainactivity = new MainActivity();
                        mainactivity.cancel();
                    }
               });
         // Create the AlertDialog object and return it
        return builder.create();
    }
}

Answer 1

做，

      AlertDialog.Builder builder = new AlertDialog.Builder(this);

Answer 2

试试这个： -

    AlertDialog.Builder alert = new AlertDialog.Builder(activity);
    TextView title = new TextView(activity);
    title.setGravity(Gravity.CENTER);
    title.setText(R.string.app_name);
    title.setTextSize(25);
    alert.setCustomTitle(title);
    alert.setMessage(msg);
    alert.setCancelable(false);
    alert.setPositiveButton("Ok", new DialogInterface.OnClickListener() {
        @Override
        public void onClick(DialogInterface dialog, int which) {
//TODO
        }
    });

    alert.setNegativeButton("Cancel",
            new DialogInterface.OnClickListener() {

                @Override
                public void onClick(DialogInterface dialog, int which) {
   //TODO
                }

            });
    alert.show();

Answer 3

 AlertDialog.Builder builder = new AlertDialog.Builder(this);

它可以工作，因为当你想修改UI时应该使用Activity上下文。除了交叉活动，你应该使用这个＆＃39;。请理解上下文。 http://androidforbeginners.blogspot.in/2009/12/context.html

Answer 4

这应该有效：

MyActivity

public class MyActivity extends FragmentActivity实现了View.OnClickListener {

    private FragmentManager supportFragmentManager;
    private Button btn;
    private TextView tv;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate(savedInstanceState);
        setContentView(R.layout.activity_main);

        btn = (Button) findViewById(R.id.button1);
        btn.setOnClickListener(this);//implemented onclicklistener (look up)
        tv = (TextView) findViewById(R.id.Textview1);
    }

    @Override
    public void onClick(View view) {
        int id = view.getId();

        switch (id) {
            case R.id.button1://listener for this id if view id is the same
                supportFragmentManager = getSupportFragmentManager();


                if(supportFragmentManager.findFragmentByTag("mydialog") != null)
                {
                    return;
                }

                //dialog fragment
                FireMissilesDialogFragment schermpje = new FireMissilesDialogFragment();
                //arguments
                Bundle bundle = new Bundle();
                bundle.putString(FireMissilesDialogFragment.KEY_OK, "ok");
                bundle.putString(FireMissilesDialogFragment.KEY_CANCEL, "cancel");
                //set arguments
                schermpje.setArguments(bundle);
                //show
                schermpje.show(supportFragmentManager, "mydialog");
                break;
        }
    }
}

---

FireMissilesDialogFragment

public class FireMissilesDialogFragment extends DialogFragment {

    public static final String KEY_OK = "key_ok";
    public static final String KEY_CANCEL = "key_cancel";

    @Override
    public Dialog onCreateDialog(Bundle savedInstanceState) {

        final String textOK = getArguments().getString(KEY_OK);
        final String textCancel = getArguments().getString(KEY_CANCEL);

        // Use the Builder class for convenient dialog construction
        AlertDialog.Builder builder = new AlertDialog.Builder(getActivity());
        builder.setMessage("Test")
                .setPositiveButton(android.R.string.ok, new DialogInterface.OnClickListener() {
                    public void onClick(DialogInterface dialog, int id) {
                        Toast.makeText(FireMissilesDialogFragment.this.getActivity(), textOK, Toast.LENGTH_SHORT).show();
                    }
                })
                .setNegativeButton(android.R.string.cancel, new DialogInterface.OnClickListener() {
                    public void onClick(DialogInterface dialog, int id) {
                        Toast.makeText(FireMissilesDialogFragment.this.getActivity(), textCancel, Toast.LENGTH_SHORT).show();
                    }
                });
        // Create the AlertDialog object and return it
        return builder.create();
    }
}