Question

我正在尝试构建一个Web浏览器，后退时必须按下上一页才能出现在退出弹出对话框中。我在同一活动中使用了两个onBackpressed方法。错误：方法onBackPressed()已在类MainActivity中定义。如何覆盖onBackPressed方法或退出时销毁应用。

public class MainActivity extends AppCompatActivity {
    ProgressBar superProgressBar;
    ImageView superImageView;
    WebView superWebView;

    @Override
    protected void onCreate(Bundle savedInstanceState) {
        super.onCreate( savedInstanceState );
        setContentView( R.layout.activity_main );
        superProgressBar = findViewById( R.id.pg );
        superWebView = findViewById( R.id.wv );
        superImageView = findViewById( R.id.im );
        superProgressBar.setMax( 100 );
        superWebView.loadUrl( "https://www.google.com" );
        superWebView.getSettings().setJavaScriptEnabled( true );
        superWebView.setWebViewClient( new WebViewClient() );
        superWebView.setWebChromeClient( new WebChromeClient() {
            @Override
            public void onProgressChanged(WebView view, int newProgress) {
                super.onProgressChanged( view, newProgress );
                superProgressBar.setProgress( newProgress );
            }

            @RequiresApi( api = Build.VERSION_CODES.KITKAT )
            @Override
            public void onReceivedTitle(WebView view, String title) {
                super.onReceivedTitle( view, title );
                Objects.requireNonNull( getSupportActionBar() ).setTitle( title );
            }

            @Override
            public void onReceivedIcon(WebView view, Bitmap icon) {
                super.onReceivedIcon( view, icon );
                superImageView.setImageBitmap( icon );
            }
        } );

    }

    @Override

    public void onBackPressed() {
        final AlertDialog.Builder builder = new
                AlertDialog.Builder( MainActivity.this );
        builder.setMessage( "" );
        builder.setCancelable( true );
        builder.setNegativeButton( "", new
                DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialogInterface, int i) {
                        dialogInterface.cancel();
                    }
                } );
        builder.setPositiveButton( "", new
                DialogInterface.OnClickListener() {
                    @Override
                    public void onClick(DialogInterface dialog, int i) {
                        finish();
                    }
                } );
        AlertDialog alertDialog = builder.create();
        alertDialog.show();
    }

    @Override
    public boolean onCreateOptionsMenu(Menu menu) {
        MenuInflater menuInflater = getMenuInflater();
        menuInflater.inflate( R.menu.super_menu, menu );
        return super.onCreateOptionsMenu( menu );
    }


    @Override
    public boolean onOptionsItemSelected(MenuItem item) {
        if ( item.getItemId() == R.id.ref ) {
            superWebView.reload();
        }
        return super.onOptionsItemSelected( item );

    }

    @Override
    public void onBackPressed() {
        if ( superWebView.canGoBack() ) {
            superWebView.goBack();
        } else {
            finish();
        }


    }

}

Answer 1

创建如下所示的方法

private void showExitPopup() {
    final AlertDialog.Builder builder = new
            AlertDialog.Builder(MainActivity.this);
    builder.setMessage("");
    builder.setCancelable(true);
    builder.setNegativeButton("", new DialogInterface.OnClickListener() {
        @Override
        public void onClick(DialogInterface dialogInterface, int i) {
            dialogInterface.cancel();
        }
    });
    builder.setPositiveButton("", new DialogInterface.OnClickListener() {
        @Override
        public void onClick(DialogInterface dialog, int i) {
            finishAffinity();
        }
    });
    AlertDialog alertDialog = builder.create();
    alertDialog.show();
}

然后像这样覆盖onBackPressed方法

@Override
public void onBackPressed() {
if (superWebView.canGoBack()) {
    superWebView.goBack();
}
else {
    showExitPopup();
   }
}

覆盖同一活动中的两个onBackPressed方法

1 个答案: